I think the M-20 was the std trans unless you ordered the M-21, at least in the world of Novas. My red 70 is a strpped down car, sold off the lot and has 3.55 w/M-20. The other 2 were ordered cars with more options and both came with 3.55 and M-21. The 68 and 69 cars are both M-20 with 3.55 gears. The M-21 seems to be better suited to gears 3.55 and up in the BB cars. Just my two bucks worth.(inflation)
TW
