How do I tell what u-joint I have? My driveshaft is scrap, so I am ordering a new one from Mancini and have no idea what size u-joint is on the rear. It's an 8 3/4 with a fine-spline yoke and a 1 1/2 inch nut....

HELP!!!

It's in a 74 Duster with a 408 stroker sb, 727 and 83/4 on factory springs.

Carnage pics to come