Who races w/OE Magnum short blocks

On the stock heads I am working on, the exhaust is a measly .575 total clearance (they say it varies). Intake side is better but still crap. That means no greater than a .515 in theory. In practice, the Magnums lose a bit of lift due to the goofy pushrod angle, say 3%, but its best not to gamble too much with dropping a valve through the motor.

The aftermarket heads have significantly more clearance, and its sort of a given that the stock heads all crack (though miraculously, the ones on my current motor are not), plus they're pretty cheap for Mopar heads, so its probably best to just plan on buying some. I believe as much as .575 can be had, but it could be more with like the EQs.