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My 50 is a 3/4 ton with a one ton rearend (whatever that means). Im not a motorhead just good with interior work. What is the best route to make it interstate worthy at speeds of 70-75 mph. It has a 292 engine and auto trans. Thanks for the help.

Do a search here in the archives. This subject has been discussed toward infinity.

You'll find a lot of people have dealt with this problem and taken various routes to solve it.

Your 3/4-ton with a 1-ton rear could be a 3/4-ton that someone swapped a 1-ton rear under... But the standard rear under your truck would be an Eaton with 4.57 gears, and the only option GM offered was an Eaton with 5.14 gears. The 5.14 gears are the only ones GM offered in the 1-tons of the era.

So I suspect that is what is meant by it has a 1-ton rear.

The easiest solution to your problem is to replace just the differential portion of your existing rear with one from a newer truck that has 4.11 gears. Unfortunately those are hard to find.

I've replaced the 5.14 geared rear under my 1-ton with a much later GM 14-bolt that has 3.42 gears. I'm also planning to run a Cadillac 500 so I'm not worried about the gear ratio, while in your case you need to make sure you chosen gears that will match your motor and transmission to your intended loads. My gears might not work if you want to load the truck heavy.

Do some searching using 8-lug or Eaton or some similar terms and you'll find much more information.

Since you already have an automatic, I would swap it out for overdrive. Sounds like the mock-up work is already done,
Scott