In my opinion a spool is a bad choice. They are downright annoying to drive on the street. Sure you like the er er er er er around slow corners at first, but it gets old quick.
I personally ditched the spool and went with a 31 spline diff. from an Explorer. It's just a heavy duty Traction-lock.
Eaton also makes a really nice diff, as well as the Auburn Pro. I think you can check out Eaton at
www.Eatonposi.com
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1988 Mustang GT
12.0 @ 121 on radials
S-trim Vortech sitting in a box!