'75 A model 8.25 worth upgrading or leave as is?

I am rebuilding an 8 1/4 for my car this winter and doing the same setup as yours. I will use a 3.55 gear set and a clutch type differential. I've seen Dana diff's for under $300. I think there the same as a Chrysler factory unit.
As far as the durability of a 8 1/4, it does have a 1 5/8 diameter pinion and there are people racing them with slicks.
I think with a street car and radial tires, it will be fine. At least that's what I'm hoping. Plus they are lighter too!