Real world swap cost

My first question is how horrible of a person would I be to put a 4 speed into a numbers 340 auto 71 Duster?

I've always wanted a 4 speed car and am getting into this question for 2 reasons. I need to change the convertor in my car as the stall is wrong and I need to have a driveshaft built as I have a poorly backyard built one.

I know most guys find all their parts at swap meets and such but where I live there is little mopar stuff at a swap meet.

So if I had to shop online and from a place like Passon or Brewers what would a realistic cost be?