. Smaller engine bay and exhaust manifolds or headers will be your biggest hurdle. Lots of different builds here and plenty of 65 Dart owners as well. I have a 66 Valiant 340 4-speed....love these cars!
What are you running for manifolds or headers. We had J heads on our 318 in the dart and opened up the 273 manifolds as much as we could...they just don't look like their is much performance possible. Tried to fit the 71 340 manifolds on the 65...not close to fitting...wish they would.