In part, it depends on what you will do with the car and tires you run. With common street tires the 8 1/4 will take a lot. With sticky tires or slicks and hard launches the torque in 1'st gear can do it in pretty fast. Axle torque and traction are the limiting factors more than HP. The 8.75 is a bit stronger but would get marginal with a 408 or especially 440 and sticky tires. The D60 would be pretty much bullet proof.

3.23 is a nice all around gear... OK for the highway and decent acceleration. Maybe keep the 8.25" and see how it goes. OD is really nice if you are spending time on the highway. Including with 3.23's. If you want to drag race probably need something like 4.10's for best results.