Differences among years...? Which engines fit?

Alright, 65,66 mustangs are roughly 2 inches shorter and 2 inches narrower than the 67-70 mustangs. The 351w will fit in the 65,66 fastback, if your interested go to horsepowertv.com and see if you can buy the tapes where they put a Tremec 5 speed and injected 351w in a 66 fastback. Also if your main concern is going to be handling i would go with the 65, 66 cars, they are the lightest of the vintage mustangs, Fastbacks are about 50-100lbs heavier than the coupes but have better handeling characteristics (reason shelby's are fastbacks), where the 67+ are more muscle cars and built for the big blocks. As for suspension find a local shop that is know for there work, there is a guy in Fontana, Calf. that dose excelent work, he changed the whole front suspension for a friend, all custom fabrication and this thing will keep up with the vetts and vipers. well thats my .02

steven