First, be patient. I've been dealing with the same scenario with my 40 Plymouth; frame is pretty good, but in order to update the suspension, you'll need to do a lot of custom work. I've also been kicking around the idea of an s-15 frame and running gear; but again, you'll need to play around with the mounts, etc. Decide what you want for an outcome, then figure time and cost. Since it is your first, I'd stick with the original, like Gasser said, if it's not too bad. Get this one done, and under your belt, and the next one (there is always a next one) try the more in depth work. Just my thoughts.

Matt