I thought this would be usefull info for anyone interested in doing one of these setup, Maybe a sticky . Anyways If you use an early diff from the strait axle, you will need to machine the splines down .130" from the inside so that the snap ring will seat in the side gear. Anyways happy swapping.

 

Although the exact amount of machining is not indicated, this (and much other interesting info on drivetrain interchange) can be found here:

http://solomiata.com/Drivetrain.html

 

And what kind of LSD unit does the SA/FB chassis have?