It's not the diff you need to worry about - it's the half-shafts! And the older they are, and the more miles/rough treatment they have had - the more likely they are to snap. Axle tramp and wheelspin on take away are the main culprits. Driven with care - 90 even 100 bhp can be handled - but many have suffered broken shafts with just the standard engine in place too.
80bhp is the recommended maximum, but torque is the enemy not power, uprating individual components just shifts the problem to another item.
What power are you thinking of and what power source
LOL that answers that Im going with a around 250 in the parts car (have the motor in my garage) was just wondering if swaping the rear axel assembly out was going to be neccasry
So it is ok will i guess i will take measurements on the Mustang Fox Body 8.8 ford rear axel and see what im into now LOL