Opinions

Need some thoughts here.
I have a 64 dart convertible with a /6. When I bought the car it also came with a 273 V8 2bbl motor and a 4 speed. I'm finally getting around to swap the motor and have some choices to make.
Currently the 273 block is magnafluxed and looks good, the bore needs to go 30 over. My issue is the availability of parts for the 273(pitons) and the cost of said parts. I have a 4bbl intake and carb for this motor.
Option two is I have a complete late 80's 360 available(Casting # on the block is 4179930). This motor may need a complete rebuild, but those parts are available and cost less. What I don't know is if the 4 speed I have will work and would the motor even work in a 64 Dart.
Any thoughts on what would the most cost effective route.
Thanks
Paul