[1969 GMC]

if you use a detroit locker, you do not need spider gears. if you want to weld the diff you could do that, however.

I have all the parts, and I took both carriers apart and swapped the lockers (I had a detroit for each one). they fit interchangeably. I didn't finish putting either one back together, though, for lack of time (its finals week for me right now).
The 14 bolt shafts are a little bit longer than the eaton shafts, but it looked like they would work. if not, there is almost an inch of spline engagement that does not even go into the locker, so i could cut the ends of the shafts.