[cmabolt]

Well, as far as you axles, it depends on what you want to do. If you don't have plans to do serious wheeling or change axle ratios then what you have is fine. If you want the truck to be used for wheeling and heavy duty type work then you might look at swapping the front axel to a dana 60 and the rear to a corporate 14 bolt. Your front differential is a dana 44. Very good and reliable. Your rear diff is an HO52 made by eaton. If you want to make changes to the front you will be able to find anything you want to rebuild, change gears etc. The HO52 is no longer made/supported so parts are still available, but hard to find and changing gears is gonna be difficult unless you go with a ration that was made for those axles. Typically your gears will be 4:10 on the K20, but there is a tag attached to one of the bolts on the rear
diff which, if not removed, will have what the ratio is. I kept the dana 44 and found a dana 60 out of a 71 K20 GMC and it was a direct swap with no modifications whatsoever. This allowed me to have a rear axle that could be easily upgraded. i changed the gear ration to 3:73

As for lift and tires I went with a 2.5 inch lift and 285/70/17 tires. These tires replaced 33x12.5x16.5 tires. They are a little narrower then what you want, but I love the stance as compared to the 4" lift many go with.

Good luck and have fun. These truck are a tone of fun to work on.
The 383 is a good idea and will save you a ton of time/money and modifications as compared to doing an LS swap. I started with the same goals as you for my rebuild and it blossomed into something very different.


Chris