What size alternator

I agree w/ TrailBeast that the ~60A "square-back" alternator should work fine. They put them in 80's FWD Mopars w/ electric fans (the main load). They started in A's in early 1970's, but lookup 1975 Dart to be safe. You need the later "2 field" electronic regulator (triangular connector w/ 2 pins), or you can wire it for "1 field" by grounding one field terminal (best get electronic Vreg $11). Use whichever style your car has to minimize wiring effort.