I'll leave out the boring details of parting out the s10 and pulling the body off the 49.
I wanted to use bushings to mount the body, but didn't want to pony up for the s10 poly body mount bushings, so I ordered some Energy suspension poly bushings for a Jeep CJ-5. 2" in diameter, 7/8" thick with a 1/2" hole...perfect. I then used pretty much the same procedure as everyone else to determine cab placement. My cab is 3.5" off the frame, and level with the flat portion of the frame under the cab. I built my mounts out of some 3x5 3/16" wall rectangular tubing I had left over from another project. Since the body bushings were shorter than the "hat channel" for the rear cab mounts, I made some simple 1/2" spacers out of a chunk of steel so the channel wouldn't rub on my mounts.
Moving the cab:
Sitting on the frame:
Up till now, that's pretty much the same as most have done.