[Formulajones]

Lust4speed is correct.

Having both M-20's and M-21's I can tell you, for an M-21 to be as quick you need to have a pretty good gear in the back. The M-20's are just quicker and you don't need as much rear gear to do it. By the time you're rolling 80+ mph for 4th gear, the rpm drop in the M-20 is less of an issue anyway with momentum.
I've run that setup with SBC's and even with less torque, the M-20 going into high gear was never an issue. And the nice thing about it, since I didn't need as much rear gear with it, it was a better highway cruiser than the M-21.


But like I mentioned earlier and Lust4speed has touched on, the TKO is a much better choice that covers both ends of the spectrum and will completely change the car and the driving experience.

I understand you'll have to do what your budget allows.