Just,
I put a 4.64 rear end out of a 2001 Nissan Xterra on my '50 3100. I was worried about it being too steep in 1st gear with 28 inch tires, and it was. I switched to 30.5" radial tires and that dialed it right in. Now 1st gear of my T-5 is usable as first gear instead of granny gear. My overdrive is .73, so my ideal highway speed is 65 MPH at about 2700-2800 RPM. I'll bet I can do 100, but that is probably a bad idea in general
