[jocko]

Thanks for sharing the pics Andy. Pic 2 looks like a non-power mc to me and Pic 5 looks like a power mc to me (or maybe Pic 2 just "looks" that way in the pic - question, is it the exact same indent as the piston in pic 5 or is it deeper (which is how it appears to me?)). Reservoir size difference is not necessarily the full reason for how you hook up the lines between the mc and the distib block (but they can be "a" reason since some mcs have uneven bowl sizes, just not necessarily in these trucks) - internal biasing is also a reason. Recall the distrib block is not an adjustable prop valve, so the order and amount of juice applied front/back is managed inside the mc and is not adjustable. If you hook up a C20 mc front bowl to the front brakes, you will be providing the opposite of factory biasing in the mc from what GM designed. In other words, a C20/30 mc uncovers/opens the brake fluid passages differently when the piston is depressed than a C10 mc does.

Or maybe a better question would be - if GM hooked up the C20 mc as depicted above in pic #2 of post 29, why NOT replicate it? Why say it doesn't matter when clearly GM hooked up the lines on a C10 and C20 differently - it wasn't a simple matter of choice for the guy working the assembly line that day? Again, I'm just talking about trying to replicate a stock system. If talking 4-wheel disks and so on, then different story. But believe you are trying to replicate a 72 C30-equivalent system(?)

As for the link to the mc you ordered, I only see C/K-5/10 in the applicability chart, no C20/30 anywhere.