65 Dart GT disc brakes

Absolutely as long as you use the 73-76 large ball joint UCA. If you're using a 65-72 front sway bar, the spindles and calipers will have to be swapped to the rear. I have the same disc brake and sway bar set-up going in my 65 Dart wagon (along with a disc brake-equipped 8.75 in the rear).

And welcome to the site!
Thanks Dartman