before doing much driving around, if any, I suggest to do a thorough inspection of the brake system and replace those wheel cylinders since you already have new ones anyway.
-pedal linkages and pivot points are all free moving, lubricated properly and adjusted properly
-pedal return spring is in place and adequate to return pedal all the way back to it's stop when the brakes are released
-cab mounting is sufficient so as not to interfere with any brake pedal linkages. felt grommet on floor of cab is not binding with the pedal shaft
-steel brake lines and all other connection points are all in good condition and not rusted at any frame contact points, retainer clamp points etc. steel line over differential is intact and shows no signs of mechanical damage (dents, extra bends, kinks etc). T connection over the differential is in good shape and retained properly. all hoses and steel lines have the proper retainers in place to keep them from mechanical damage
-rubber brake hoses are all in good condition and do not show signs of age/cracking when bent/flexed. crimp connections on hose ends are all in good condition and no signs of leakage
-park brake linkage is all connected, free moving and operational. park brake linkage should be backed off prior to brake drum removal and any brake work, like wheel cylinders, is done. then, after the brake work is complete the brake shoes should be adjusted as normal. after that the park brake should be adjusted. it is important to do these steps to adjust the brakes properly otherwise the park brake adjustment, if not released, can affect the service brake adjustment. if the park brake is not adjusted properly after the service brake adjustment is complete then it can have an affect on brake performance. some guys will simply not have a park brake and then complain that they always need to pump up their brakes. that is because the park brake adjustment keeps the brake shoes from returning the wheel cylinder's pistons all the way back into their bores. when this happens it takes one pump of the pedal just to get the pistons out far enough to make the shoes contact the brake drums
-I will leave out the part about wheel cylinders because you have new ones to install but will add that the steel line connections are all tight and not leaking/kinked/twisted as can be the case sometimes after brake work has been done. a lot of times the steel line gets twisted because the flare nut is seized onto the steel line. if it looks suspect simply replace the line, they are pretty cheap anyway.
-brake shoe lining and drum max diameter are within serviceable limits. no lip is present inside the drums
-brake backing plates are in good condition and do not show signs of wear or grooving in the brake shoe contact areas
-brake hardware (springs, shoe hold down hardware, park brake hardware etc) is all in good condition and complete
-rear axle seals are not leaking, differential vent is serviceable and not plugged (plugged vent causes pressure build up and makes axle seals leak all over the brakes. oil on brake shoes actually makes them stick and causes the wheels to skid rather than making the brakes slippery like one would think)
if doing the wheel cylinders I would recommend disconnecting the steel line at the master cylinder and at each wheel cylinder and collecting any fluid that will drain by itself by gravity. then, before installing any new parts, get a can or 2 of brake cleaner and blow out the steel lines from the master cylinder end on down until clean fluid comes out each steel line at the wheel cylinder ends. this will keep any debris, rust or other contaminants from getting into your new wheel cylinders. if you have an air compressor you can use a rag over each steel line (this will keep the fluid from becoming airborne or aerosol'd), held on with tape or what have you, and then use low pressure air (like 5 psi) to help you clean the lines of fluid or brake cleaner. remember that brake fluid is like paint remover so be careful not to get any on the painted surfaces or your skin/eyes etc. dot 3 or dot 4 (like what would normally be used in these systems) brake fluid also likes to absorb water so never use an old can or especially an unsealed old can. I assume the murky fluid you seen is simply dirty fluid from a dirty system, those old master cylinders didn't exactly have a great sealing lid on them and the master lives down on the frame where dirt/mud/moisture can collect. that is the reason why manufacturers advise to have the brake fluid flushed yearly or at least at every brake job. this is especially important for vehicles with disc brakes, those calipers get stinkin hot and the fluid can actually turn color from the heat. dot 5 fluid is silicone based and doesn't absorb water so some guys will use that for vehicles that sit around a lot. the whole system needs to be flushed and cleaned prior to using the dot 5 fluid though
anyway,
do the inspection and get the related parts required. hoses, steel lines, fluid, hardware kits etc
spray some penetrating fluid on the holes in the brake drums where the wheel studs and axle flanges come through on the rear brakes. you can help this along a bit by tapping the brake drum between the wheels studs to set up some vibration and get the fluid penetrating the area faster. the front brakes need to have the wheel bearing hub assembly removed to access the brakes I think-it's been awhile so not totally sure on that
back off the park brake
back off the star adjuster wheels so the shoes have a chance of clearing the lip on the drums
then pull the drums, spray down the whole area with some water in a hand pump squirt bottle (you don't want to inhale any of that dust or sweep it up later and get it airborne) and see what you have
take a pic of the system set up before you disassemble so you can reference that when it is assembly time or have a manual with you to ensure you get it right
if using the old drums and shoes you can use a drum sander to cleanup the brake drum surfaces and some brake clean and course sandpaper to clean up the old shoes. remember to wear respiratory protection because brake dust is carcinogenic. an automotive machine shop or a parts store that machines brakes can probably measure the drums for free to ensure they are within the wear limits. if there is any grease or oil on the linings it is rcommended to fix the leak first then replace the linings. the material is like a sponge and it may look clean after using brake cleaner but when the brakes heat up the grease or oil will be released from the lining material and you will have the same problems right back again.
https://www.harborfreight.com/4-piec...set-35455.html
if replacing the shoes and having the drums machined remember that the new shoes will not fit the over sized drum well. some places may still sell oversized shoes-these have a thicker lining material attached to the normal shoes. they are actually meant to be arced (ground down) to fit the size of the now larger brake drum so if installed right out of the box with no re-arcing done they may be a tight fit. they will also not contact the drum like they should so they will need some attention for the first little bit until they "wear in" and fit the drum. the re-arcing process is manual at that point so they will need to be adjusted as they wear in. you will also not have great brakes until they do wear in because the whole shoe friction material surface is not contacting the drum, only a small part of it. sometimes it is a little more money to buy new drums but worth it in the end. use some brake shoe lubricant on the backing plates where the shoes contact (small amounts) and use some anti seize compound on the star adjusting wheel threads (unscrew the whole thing, clean and apply). use anti seize on the axle flange as well before installing the drum. this will help with the seized on brake drums next time.
when adjusting the brakes after assembly tighten the star wheel until the shoes are tight against the drum, then back off the star wheel 7 notches. then adjust the park brake.
maybe some info here for you
http://chevy.oldcarmanualproject.com...esto/index.htm
hope that helps somebody out there. sorry it got long winded