he swears this car with that combo will run 12.40 in the quarter mile
If he's talking MPH, he's right. If he's talking ET, he's wrong.

He essentially put a cam in a stock motor. That gives him not enough horsepower, the wrong gear and the wrong converter. If two wrongs don't make a right, three certainly don't.

My advice . . . don't argue with him. Just tell him good luck and ask to see the timeslip.

As they say, it's like wrestling with a pig. You both get dirty, and the pig enjoys it.