Hi first post here - thought I would ask a question re/ my stock '54 235. I am looking to change out my current rear end -

I have a chev 10 bolt. I am told it has a 3.73 ratio. I am changing because of width and some other issues .I also have installed a T -5 trans although I am not sure of the ratio right now. So what I am trying to figure out is what the best rpm range for hiway driving would be - somewhere bet. 60 - 70 mph
Thanks,
Surf dude