The Idea!!!!

A stock srt-4 neon has a curb weight of 2900 pounds. A stock 68 Dart 4 door has a curb weight of 2866 pounds. Subtract the weight saved by using glass body parts and the fact that the 2.4 weighs considerably less than a slant 6 and your car should be a few hundred pounds less than a stock neon. I'd think 30mpg should be very doable! But I've never messed with anything like this so I wouldn't know for certain. I do know that there is a 67 valiant 4 door in a local 'yard that I want to do this very swap to some day tho! So get it done n let me know the results!! Lol