To buy or not?

Nice cars both of them!

There is only one good solution to this:
-Souped up Dart Sport 340 Weekend Warrior
-Stock Dart 318 Daily Driver

Kidding aside, I'd say it depends on the cost involved and most of all what you are really looking for. The Dart would be a very nice little driver with some work, the Sport could be a really cool "muscle car" with some more work..