Swapping trucks is very possible also. It doesn't have to be that year either, as up to 1994 had the same basic chassis. Notice mine is a 1991. It was an 4.3L gasser with an automatic. I bought this truck specifically to switch it over to a diesel w/5spd. Lucky me, the automatic driveshaft fit right into the manual transmission, without any modifications at all.
If you plan on keeping it far a while, and the current truck is "iffy", then use something you know will last for a while.
My guess is the most complicated part of the swap will be the wiring, and that really isn't hard for someone that is good at it. I used the stock wiring harness and used just the wires I needed.
I have a big, long-winded <img src="/forums/images/graemlins/cyclops.gif" alt="" /> post here somewhere on the whole thing.

I hope this helps. <img src="/forums/images/graemlins/kewl.gif" alt="" />