rdbates,
I have done it before and it pretty much is
as simple as you described. I made new cross members out of rectangular tubing, except the
front x member, which I took a section out of the center. I'm guessing you want to still keep the 3/4 ton rating, but have the ifs as well.
An S-10 frame and running gear will emasculate your 3/4 ton truck. If you want to do it, go for it. I have a chassis jig that I built for doing this kind of stuff, but it certainly can be done w/o one on a level garage floor and some solid jackstands. Make sure it's very level, not tweaked when you put it back together and take lots of diagonal measurements to keep it square. This is not a hard job for someone with good welding skills and mechanical aptitude. You could even make the new x members to bolt in and just have to weld on the front one.
Good luck with it.
