Dalyman,
The stock gears in a 57 1/2 ton are 3.90:1. 3.73:1 gears would hardly be worth the expence of changing rear ends. The only gears available for the stock 55-62 chevy differential are 3.90 and 3.38. Changing the diameter of your tires will drop the rpms further than changing the gears.
My honest opinion is that an od transmission swap is easier and more effective than a rear end swap. If your rear end is excessively worn, that is another story.
What engine/transmission combo are you running now, and how do you drive the truck?
