I don't have a tac in the ramcharger but my math says right at 2000 rpm at 60 mph with the gearing and tire size. I don't plan on changing my gearing because i would like some mileage from the truck and the only thing i plan on towing is my little jon boat. 390 is more then i need but its nice to have a little extra in reserve. If i have to hook onto the car trailer my 408 powered '98 ram comes outta the shed. That 4" crank will surprise you and roll smoke off the 285-75-r16's. The 408 pulls 16 mpg if you don't act like a teenager. The only thing i really miss about my cummins is the 22 mpg.