Probably not your best option.
The brake drums have been hard to get though apparently the 3/4-ton ones are now being reproduced.
The 4.57 gears will limit your highway speed.
You should be able to find another axle that is a better choice if you are committed to a change. It sounds like you're changing the rear because you need to change the transmission. An open drive type SM420 can be converted to torque tube type easily and that might be your most direct solution.
