1/2 to 3/4 swap?

[True Grit]

I use my truck alot, and i would like to convert it to 3/4 ton.Problem is there are not alot of doners around, but i'm told that i can use alot of parts from the 73-87 models, is there any truth in this?I'm told i can use the spindles if i change the ball joints and outer tie rods. What about the front coils? By the way it's a 71 GMC (rear leafs).I can find a rear end from a later model and replace the spring mounts. Any help/advise would be great. Thanks in advance.