My other Early A ---65 Dart post
I dug through my garage and found the drive shaft for my 66 dart. Its a few inches longer than the 67 but the front yoke seems to be the same on both. Its from a v8 4 spd car so its thicker in diameter of the shaft and the rear u joint has larger caps on the shaft. I bought two new u joints . Front one is precision part # 315 and rear is 347. The 347 has the larger caps to fit the 66 shaft and the smaller caps to fit the differential yoke.
Special thanx to fabo and its members for having the u joint info and part numbers i needed. The guys at the parts store weren't very knowledgeable of what i was trying to do