Sounds interesting. Are you going to be able to go back & forth between direct drive & overdrive? How will you shift? Or is this a permanent overdrive? The SM420 has rather wide gaps in gear ratios. I think 30% would make it hard to accelerate. Unless the motor has alot more power than stock. I think it would work if you can shift in & out of OD, splitting the gears like a stock 3spd w/OD. Just shifting in & out in top gear to reduce rpm's would be great. I have 3 trucks w/SM420, so I'm curious.
