67-69 barracuda 4 speed parts fit 70-72 dart/valiant?

I can only suggest you find out exactly what the origin was. I talked with a guy who bought a 71 Duster and found the 4 speed trans installed by previous owner came from a 1st gen' / pre 67 A-body.
Small differences at pilot shaft and bushing, speedometer cable, etc.., made for a few small headaches.
Good luck