Honestly you do not need the fixture.
get a good solid bar.
make your own pucks that fit snug inside ends of housing with a hole to fit the solid bar in.
i have a dummy center 741 chunk i also put in the center with pucks to keep the solid bar straight, but in reality you dont really need that center support.
measure alot.
I then take a 2 good size angle iron and clamp it to the housing. Then slide the new or used ends between the angle irons.
The angle iron keep the outside straight. The bar keeps the housing centered.
I also make a good chamfer where the two ends will meet and fill it full of weld.
I have done my own 8.75 and it has seen some slicks and about 500 foot lbs of torque.
I also have a narrowed dana 60 that i done just in case i pretzel the 8.75
I buy new axles from moser
