[Formulajones]

Lust4Speed is correct, the M-20's are generally quicker and don't need as much rear gear to do it.

The RPM drop in 4th isn't even that detrimental as you already have momentum working for you. Simple physics. It's the getting moving part that is a bigger player.

Many guys in the 60's figured this out when ordering their muscle cars and opted for the M-20 with 3.73's and even 4.10's. Many Z cars were built this way, You'll also find in PS racing that the M-20 is more commonly used as it's a bit quicker. Guys that wanted the M-21 and knew this would order their car with 4.56's and even 4.88's if they knew they were going racing.

My M-20 car with 3.55's will absolutely blow my M-21 car with 3.73's in the weeds and they both make about the same power. The M-20 with 3.55's simply has better gear multiplication up through the gears.