I believe there are only really two generations of Darts. The narrow body 63-66 and wide body 67-76. There is also more in common with the 61-62 Lancer than the fat darts of 60-61 and 62, so they really don't count!
I lump all the 67-76 Darts in one category because you can literally swap many parts. You can take a 67 hardtop roof and put it right on a 76. Sure the doors changed, but you CAN make them work. The 67-69 fenders and the 73-76 fenders CAN be swapped out with not much work. Heck I had to tell an original owner of a 69 M-Code Dart GTS that he had a 74 fender on his car, he didn't even realize it after the car was wrecked and a body shop fixed it!
