Redthies,
I would love to put in a Cummins. In fact that was my original intent with this project. However when I saw the work that I would need to do to make that happen, it kind of dampened my enthusiasm for it. I plan on keeping this Burb for a long time. Maybe after I get tired of one engine, I can throw in a Cummins with all the axle and transmission upgrades needed. For now, the quickest upgrade power wise would be to just cam up the 350 but I'm still left with a 350. A Cadillac 472/500 can be had for 200-800 bucks used and parts are reasonably cheap.
In terms of plug/play and time involved, I think the Caddy swap is the best option for my circumstances based on all the evidence. All your input and experiences is greatly appreciated.