Welcome to the forum Jeremy
I don't have any experience with the Eaton HO32/33 with that much power. The most I had in front of one was a 300hp 327. As with any differential it's not so much the hp or tq but the tires it is turning and how well they get traction. You can likely put that much power to that differential with skinny tires and be okay. But with some wider sticky tires, you will definitely find out just how strong it is. Most of the Eaton HO32/33 differentials came with 3.90 gears. There was an option of 3.38 gears and that is the only aftermarket gear available now. You can buy bearings and seals, but that is about it. There should be a code stamped on the passenger side axle tube. The '55-'64 cars did have a similar differential but as far as I know, nothing interchanges. If it were me, I would just upgrade to a truck 12 bolt. There is a lot of aftermarket support for those. I do make trailing arm mounts if you do decide to change differentials.