He swears it’s true. So if the tach is accurate then let’s check that cam and valve springs. They must be aftermarket replacements. And the carb would need to be richened up. What about the ignition box, is it stock?
I cannot see a stock cam, valve springs, carb, and ignition box making power to that RPM unless it was a manual transmission going downhill, and then downshifted.
a stock big block won’t pull to 6500 Either.
Leave max wedge and hemi out of this silliness.