When you do the motor swap change all the valve springs to 6.1 Hemi exhaust valve springs (Use them for intake as well as exhaust) They're stronger.
Check local scrapyards for a cheap motor, or rebuild the one you have. Get a shop that is well known for good work, it pays off big time down the road.

For rear diff, get that posi replaced with Auburn or Detroit.

For tranny, it might need a rebuild some day, but it's substantially cheaper than the engine rebuild anyway (At least around here)