doing the math (unless I did something wrong) if your engine spins 2800 rpm @ 70 mph with 3.42 gears, changing the gears to 3.73 would mean 3053 rpm @ 70mph. Dave asked about 60 mph, 3053 rpm @ 70mph equates to 2617 rpm @ 60 mph.
And I have the same 31x10.5R15 Tires you do. With the look homer52 is wanting, I don't think he'll have room for a 31 inch tall tire or one would fit. He's told me a bunch of info on his truck, I didn't mention all the information in my post.
I wrote my post assuming his tires wouldn't be any taller than 28". I could be wrong though.
