Lots of options and none of them simple. If you put a 44-4 ( Continental 260 ) in it you need the use the 44 radiator and bellhousing. If you use the 6 cylinder you need the radiator, bellhousing and face the hydraulic problems. Trying to rebuild the stuck 333 engine could be costly because of parts. If you are mechanically inclined, I would suggest pulling the head and oilpan off to see what you are up against. If you are lucky you may get by with a new set of rings and maybe some bearings. If the sleeves are worn or pitted you may need look at your other options.
If you decide to trying rebuilding the existing I do have a few new and used 333 parts laying around. Email me if you are interested.