Rear end advice for racing with a 4 speed

450 hp with a 8 3/4 is do-able with an auto trans. With a four speed I would plan on a Dana 60 or Ford 9". A Ford rear might not help resale value (if that means anything) but a Dana certainly will.
You can spend money on the 8 3/4 to make it stronger, but it still might not be strong enough, and upgrades are expensive.
If it were me? Id get a strange 60, and sell the 8 3/4 before you break it again.