355 to 308 ratio?

[Precisionw900]

(04-18-2022 )Waterloo Wrote:  I'm running the 3:42 with the 600hp 18 Spd, and can tell you your mileage will not differ by much at all, if any. I get my best mileage running in high 7 at right around 60 +/- 2 mph. The rpm is right around 1500 - 1600. I'm pulling a van, mid roof, so my fuel mileage is usually around 6.5 mpg, my truck is a bit of a pig, a heavy pig. I would stick with what you have and keep that money in your pocket. Like Rawze and others have said, you will just beat the motor to death... And having been through two in frames in my ProStar, you don't want to go there.

I’m running same set up except set at 550 and you are right. The high side of 7th or low side of 8th is the sweet spot, can run 60-65mph and keep below 20 psi of boost. I only use the high side of eighth unloaded on the big highway. I would never step over a 3.70 with a 10 speed.