A 91' d60 would be a King Pin, that is hard to miss.
The 44 in 91 would only be a ball joint axle.
The 44 cover measures 9.5" across, the 60 is 11"
If it is a king pin axle it would not be a 50, maybe a 61.

Both the 50 and the 61 are wastes of space.

The rear will be a 30 spline 60, once again a waste of time.
It is a myth that a 30 spline 60 is stronger than a d44.
Chromo 30 spline 60 shafts are still not stronger than a 44 with stock shafts.

If the front is a KP 60, it still may need a cut and turn to work properly. Pinion to caster angles are close to the 90 degrees from each other, bad.
The Chevy kp 60 has 10D pinion and 6d caster, much better.

SD