Same as a X,J,U, etc....A 340/360 head. Valve size of an X is a 2.02-1.60 and sometimes the J as well I'm told though I never seen one stock this way. All others should be a 1.88 intake and 1.60 exhaust though nothing in the MoPar world is in stone.
They all flow about the same reguardless of letter except where the valve is bigger.
