My owner's manual says your 46 diff is a 6.17 which is almost the same as the high end of the two speed diff which is 6.03. You could try to put 22" wheels on the back,that would help some. I don't know if it would be a good idea to go drive 60 MPH in a truck that was only designed for 45 MPH. My 46 didn't even come with shocks!
