ET Report Card on the Speedmaster Heads

Yes so much can be won or lost with tire size. Many years ago when my 340 was fresh out of the motor shop I ran an M1 single plane within 850 thermoquad BF ta 265 50 14 they were about 24 and 3/4 inches tall with a 391 rear end and a 509 purple cam it was a match made in heaven but definitely not a freeway combo