I ran my '64 Pontiac Tempest down the track a few times, ran 20-flat at just a tick under 70 mph in the 1/4 mile. Still had the original 140HP 215-inch straight six (same as a Chevy six except for cubic inch size, 3.75 bore X 3.25 stroke), 2-speed Super-Turbine 300 (same 1.76 low gear as most Powerglides) and 2.56 rear end with 205/75-14 tires.
It never got out of low gear at the track, I shifted in to high gear right at the finish line. This calculates to 4060 RPM if you don't take converter slippage into account, should be a few hundred RPM above that in actuality. These engines in bone-stock form are usually all done by 4400 RPM.
The 215 was kept in a decent state of tune, but could have been better. Always retuned an average of 20 MPG in mostly 75-80 MPH freeway commuting.
