The IFS used '63 through '87 on pickups and a few years longer on Blazers and Suburbans is the same basic design. Depending on exactly what years you are dealing with some holes may need to be enlarged, but its basically a bolt in swap.
Starting in 1971 disk brakes were available, so all you need do is find a '71 or later and swap the complete crossmember with suspension. I'd subbest looking for one with power steering and swapping that too.
You can find these things nearly free, so establish a budget and look for the one in best condition that you can afford. Remember even the newest ones are nearly 20 years old and likely to need ball joints and bushings.
If you could find one in a wrecking yard that already had dropped spindles that could be your best bet for doing this on the cheap, though the drop spindles aren't real expensive.
If you have more time than money I'd suggest spending time finding good parts cheap.
The disk brake trucks are all 5-lug, so you are either going to change the rear also, so have both 5- and 6-lug wheels going this route.
