Have 340 swinger and 71 scamp... Do i cut up scamp 4 dart? Or build 340 scamp clone?

How bad is that 340 Dart? Any pics? Looks like you must have had some up at one point, but I missed them.

My .02, If you need new metal for the Dart, buy new metal. Chances are, when you blow the Scamp apart, the metal may not be as nice as what you think you have. OK for a driver, OK as installed, but just not worth reusing on another car. I know it's only a /6, $500 car, but it looks like it would be a nice project or driver. Keep the 340 stuff with the Dart, put a 360/904 in the Scamp and drive it while you restore the Dart.