From what others have posted, I think the early Chevy S-10 frames and drive trains are a good replacement for the originals.
I just did a little research on this, and a rear axle from a 4x4 S10 is about a perfect fit as far as width. Very close to the tread (distance between tire tread centerlines on the axle) on a 47-55 Chevy. I saw one on our local craigslist for $250.
Didn't look into the frame issue though.
