Anybody consider a V6 swap?

I think it depends on what is already in the Dart. If it is a V-8 car then the V-6 will drop in. However if it is a /6 car you'll need motor mount adapters (Schumacher Creative Industries?) or a V-8 K-frame. Putting a carburetor on the V-6 will be more straight forward than trying to make a fuelie out of a '68.

If you go with the V-6, you'll need a long fan shroud or an electric fan to cool the engine. If you have a V-8, the bellhousing will fit the V-6 with no problem. Otherwise, you'll need to swap the bellhousing or transmission to make it work.

IMO if the car is already a /6, leave it as a /6. There's plenty of aftermarket support to get quite a bit more power out of it. If it was a V-8 car, then the V-6 with a 350 cfm Holley makes more sense. Aftermarket go fast parts for the V-6 will be more limited.