I have a one 62 one ton which at one point had a 5.38 rear end and 30 in.tires . I installed a over drive with a .63 final ratio and traveled many highway miles at the 75 mph range without issue . I'm not a techie but I figure if a crankshaft can turn at 3000 rpm for long periods a pinion shaft should be able to as well.

John

good planning is no substitute for dumb luck