Taking a poll about which drivetrain I should use

I have 3 options here. The first is to take the 318 and 904 out of my 70 duster and have it rebuilt. Right now the car is numbers matching with the exception that I am adding buckets and a console (shifter is already on the floor) and am adding power disc brakes to the car.
Option 2: take the 318 and 904 out of this 74 dart that only has 36,000 original miles on it.
Both motors run now, but the 904 in the dart actually shifts right and the dusters does not.

Option 3: sell the drivetrain out of the dart to pay for the rebuild on the dusters original drivetrain.

Is a 70 drivetrain better than a 74 would be my only other question, other than resale value?