1963-1966 Dodge Dart Buyer’s Guide for Restoration

I'm not sure what the answer to your question is today. But as time goes on and the cars get more and more rare, I've got to think a car with the original drive train will eventually be worth more. If you could bolt in the V-8 while retaining all the original parts that might make sense, but I think you have to modify the firewall to get a v8 into a 63. Besides I think slant sixes are unique and interesting.