70 MPH in a stock AD truck is pushing way past the safety sensibility limit. I recommend that you drive somewhere that you can't harm anyone including yourself and accelerate to 45-50 mph and slam on the brakes and see how long it takes to stop and how it handles during an emergency stop. Then think about what would happen with the addition of some loose gravel or slick road conditions. I understand what you are trying to do in terms of being able to go more than 45 mph without redlining the engine. I put a late 60s/early 70s six lug 12 bolt rear end with 3.73 gears out of a 1/2 ton truck in my 50 1/2 ton and it is much easier on the engine and I can keep from being blown off the interstate.
