Engine is good for high 11's or better with a decent chassis/converter.

Get lots of initial timing on it. Get a bushing for the msd to decrease mechanical to 10 or 14 degrees. I'd bet it will take 24-26 initial timing.

An LD340 or air gap and 750dp will kill the M1 down low and be equal up top. Make the converter work harder too.

3.91's, try a shorter tire. A 26" tire would help a lot. 28" I'd run no less than a 4.30 and better a 4.56.