Want to get the most I can out of my Stock powered 283 Nova (67) with 3.08 open rear. may go to a 350 (290HP) crate motor some day but nothing more than that. I have 2 Muncies to choose from a M20 or M21 both are good but don't want to do it twice, the M20 2 ring 2:52 1st and the M21 1 Ring 2:20 1st which one will make it leave the best and be better all around thanks. It's just a show car tired of the Automatic now!