4.10 is all a 300 needs. 3.73 is better for highway use. I run 4.11 and see about 2,300 at 60 mph, and nearly 3,000 at 70. Give or take. I think my truck's best cruising speed is at 50 mph. She runs pretty good though with the lower gears around town and under 50 mph.

 

Thank you 6CylBill.

Does anyone out there know what the ratio is on a C1 (on the door sticker) axle?

 

i think the best possible combo for a 300 is 4.10 and a M50D. it pulls like a **** in 1st, pulls in second, then 3rd it starts to get higher and finally your 70 mph at 25/3000.