New to me 65 Dart Gt, what to look for

There's no end of money that can be spent on making the car better. See this post for upgrade order-of-operations philosophy.

Tune-up parts and technique suggestions in this thread.

Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download.

You'll want to get the three books (plus-minus, depending on your level of general old-cars knowledge) described in this thread.

Parts sources: here for a start.