Well Im considering doing an axle swap. kinda not happy with the weight raiting of my truck (in signature). Its 6600GVWR 3700Front 4000Rear; 14bolt gm semi floater 6 leafs. So while looking for something else in a parts yard, i found a 89 gmc 5.7L crew cab. it had no emblems, but had failed emissons paperwork in it saying its a C2500. (forgot the vin to decode) So im checking it out, and behold..a gm 14bolt full floater axle. so wow..got me thinking about what it takes to do a swap. that truck was 9000gvwr and 6084rear and 9 leaf springs.
immedate differences is a way larger brake drum and I would have to relocate shocks from outside the fram to the inside.

So..im looking for opinions if its worth doing, any advice, anything at all. This is listed in the 6.2 post since one of my main questions is about the brake system...such as if the master brake cylinder has to be changed(mines JD6 13"/2.5" brakes)....or any other parts of the brake or any other system. I know I will have to match the ring/pinion to my front(the other has 4.10 in it ..so other then that feel free to ask any questions and give any info or advice. Thanks in advance and look forward to hearing replies.

I've done it by myself and without instruction. I blew the 10.5" 4.10 rear in my '93 HD and I had an old '79 HD with a 10.5" 4.08 but the axle perches, shock mounts and bumpstops were in the wrong places, and styled different. I cut the necessary parts off the blown axle and welded them in the same spots on the replacement. I used one/two 3 ton jacks to move it around. Two is easier but one works if you balance it on the pumkin. Once it was all bolted in, rea doing the e-brake cables was the last part, as they'd changed design and didn't fit.
If the trucks have a similair frame width and are close in years, it's a matter of hardware.

http://www.chuckschevytruckpages.com/images/rearend.jpg

Thanks qm. Anyone else have any suggestions, comments, warnings?
**Anyone have any idea how or if even possible a JD6(13"/2.5") 6.2L brake system will work on this said full floaters 13"/3.5" brakes?

I did some measurements on it today, the shocks are moved from outside to inside the frame because of the different size of the brake drum. To make the tires fit, they shortened the axle which lost the room for shocks. Causes a problem since my trucks dual exhaust is in the way. (wouldnt be later since when this exhaust goes bad, been thinking about under the door side pipes)
Also seems maybe its not so much the axle that gives the truck its weight rating but the leaf spring setup as well.
-donor C2500 crewcab (fullfloat) GM 14blt GVWR9000 Rear6084 9 leaf long
-on ebay K30 6.2 singlecab longbed (semifloat) 14blt GVWR 9200 Rear 6084 9 leaf
All of this is confusing for sure, so many different setups. I figured singe the full is a stronger axle would be able to hold more weight. And how come a whole lot more 3/4 ton fords have full floaters and so few chevy/gmc have them??
---I read on a 14bolt site that because the full floaters axle shaft does not support the weight of the truck, unlike a semifloater, its only job is to transmit torque. question-So would you actually be putting more power to the wheels? Comments/opinions?

Brakes may be a different size. Different wheel cylinders. Different braking power in the rear. Front will still be the same.