I recently saw a '53 Chevy built over a '74 International Scout 4x4 chassis, and it uses the engine and driveline from same. However, from the outside, you cannot tell any different from a stock Stovebolter. Very nice restofication.
Might be less work than strengthening a stock frame and upgrading it to 4x4. I'd love to have 4WD on my truck, but it has to be done right. I've seen one all jacked up with 4x4 under it and that WASN'T done right. Might have been functional but it was ugly. That's what changed my mind about doing a similar 4WD conversion.
Nope, if I can't get it to tuck underneath well, I'd rather keep it 2WD.
So yeah, dropping the body on a modern frame might be the easiest way to get those results.