Outer Limits 4x4 Board

i am having trouble finding another rear diff centre for my 3.9 ratio 1984 N/T sierra. The one in it is welded so i cannot rebuild and i can only find a 4.1 ratio secondhand.
Does anyone know if the spider centre is interchangable between the 3.9 and 4.1 ratio diffs.

This way i can buy a 4.1 and just use the spider gears of it.

Does this make sense/work????????
Does anyone have a diff centre i can buy???

good luck there arent too many left but they come up for sale every now and then. I sold a pair of 3.9's for $500.

tell me about it. its the last thing i need to get her on the road. thats why i am desperate for alternatives.

Anyone got any ideas??

Use an open centre out of a 3.7 WT diff.