I've not ever heard of a road racing team using the M20. I'm not saying it couldn't have happened but I'm not aware of it.
Because of the relatively small displacement, the torque range is narrower and higher up the rpm scale. If there is a larger
jump between each gear ratio, the engine speed could fall out of the optimal range and that would have an adverse effect
on lap times. You are rarely using first gear in a road race except for the start or leaving the pits. Ford did homologate a lot
of different gear ratios for the transmissions but they had a huge amount of money that they openly threw at their racing
program and Chevy was not allowed to race at that time. Ford would rent track time ahead of each Trans-Am event and dial
in a car in terms of tranny ratios and rear axle ratios (plus spring rates, etc) and Penske would do this as well but I've just
never heard of an M20 being used. In 1970, the SCCA allowed race teams to use rear axle and transmissions from rival
manufacturers. This allowed the Chevy teams to use the Ford rear axles and transmissions and of course it is much easier
to make a rear axle gear change on the Ford axle than on the Chevy. Prior to that, most independent Chevy racers were
probably just running the same rear axle ratio regardless of the track and doing the best they could. Penske could afford
to make a gear change in his rear axles or have a few spare trannys and axles on the truck but most of the independents
couldn't afford that.