im looking at buys some 4.10 gears for my truck, would mustangs with the 8.8 rear end be interchangeable with my truck?? Also what size spline would i need with a limited slip for that rear end?

 

I think the gears interchange just fine. Mustangs had 28 spline axles until (2000?) when the Cobra got 31 splines. The 8.8 truck has 31 splines I think.

Just make sure what you have. The 5.4 trucks got 9.75" rear gears.