cant speak to exact,, but "most" of all the "new" ray stuff is with an m1 casting,, and "most" of charlies stuff is with an m1 casting,, more metal around intake port,,, better exh port, deeper long side,, m1 head is a few lbs heavier than an m head
i asked about running an m1 head about 2 years ago and was told to grind the 1 off at the end of the part number
i just looked,, they took the weight off the aluminum head,, this is soooooooooo stupid
