@scooterabc - Great insight, thanks once again for all your thoughts! "get the current mechanic to specifically list why he thinks a full rebuild is in order" I'll do that and get back with y'all.

@cdodgyd - All good info, thanks for the additional details

@tomguy - Good perspective on Diesel. I've replaced about 70% of the rubber that I could find. Surprisingly, most of the rubber was honestly in good condition, but I replaced the majority of it anyways, just to be on the safe side. "Your bottom end is unknown" so true, and this is what really concerns me. And why I started out this discussion with should I sell or part it out. The car has potential for sure, but the unknowns are starting to concern me. Every time I fix something I find another issue, which I expected to a certain extent with an old car, but the engine having issues really made me take a step back. Yeah I'm clueless on "what engine" if I did a swap. Any further thoughts on this point? What would you do ideally for the engine swap?

@bwhitmore - Okay good to know. A couple more votes for keeping the current engine. Thanks!