is this a good deal?

[mrboyy17]

http://yakima.craigslist.org/pts/1702487328.html
is this all i would need to make my 1/2 ton into a 3/4 ton?  i need to be able to haul a whole yard of rock and stuff and my 1/2 ton wont cut it.  how hard would the swap be?  my truck is lifted 4 inches right now, but do you just put the same springs on or do i need different springs too?
mark

[The Lady In Red]

Well I dont know what year your truck is, nor do I know what year the seller's rears came from, but when I interchange an 86 k10 frame, I show the frames being identical between k10 and k20's from 84-86, both GMC and Chevy. The 5-leaf springs show to be the same, so if that's what you have, you are in luck.  Of course, having more info on the vehicles would help

[VileZambonie]

If they're in good shape that is a good deal