What engine for my new Town Panel?

You will have to fab motor mounts about any way you go, along with exhaust and transmission mount. That being said, if it were mine I would go with the lowest mile 5.7 Hemi that I could find from a newer 4WD truck. Call Chris at Hotwire, and see if he has a harness available for the 8 speed automatics, in case you find a mashed parts truck with one of those in it. I know he makes one for a 545RFE. If the front yoke on the newer transfer case lines up on the same side as your existing front differential, jerk all of the old stuff out and use all of the new stuff. If you're really wanting an 833OD, get one of Jamie Passon's 833OD conversions instead of trying to us an original one. The original 833OD would never stand what your goals for the truck are. Good luck, and have fun.