Thanks. The only number I see stamped on this head is "542"... not sure what that means, if anything.
The valve I pulled out is 111mm long, tip is 4.5mm, and the machined surface on the head is 23.0mm on both ends. I'm just using a metal tape measure, so there's a little margin of error here. I'm mostly concerned with making sure this head will be legal after another resurface, rather than shaving it down any more for the purpose of power. I have early pistons, so I would think that I have some room to play with, but just want to be sure.
Thanks!