8 3/4 pinion splines

crackedback said
The lower pinion in your picture isn't a 741 case pinion.

That's a 742 case pinion.

Are you sure? Looks like a 741 with a spacer on it to me.
There are basically four stock Mopar 8 3/4 rearend yokes. Big and small u-joint, and coarse and fine spline.
The yoke needs to match your gears and u-joints.