Drive shaft

Agree with Dana67Dart. Make sure what you have.
If it helps, my '69 Barracuda shaft is like 49-1/8" between joint centers if I recall. Both ends use the 7290 U-joint. The slip yoke spline is a 30 count.
I believe a Dart shaft is longer.

Brewer's Performance - Mopar A833 4-Speed Transmission and Component Specialists
Brewer's Performance - Mopar A833 4-Speed Transmission and Component Specialists