How do I measure cylinder to see how much has been milled off???

moper said
Measure that thickness from the head gasket surface to the machined flat and it should be 1" if it's not machined. Again - with the varying casting quality, and the crazy factory machining I'm not sure that's 100% either - but I'd much prefer measuring two machined surfaces than try and make sense of any as cast surfaces.

66fs said
These are the Tooling Pads used to machine the head surfaces. This is the best way to try and determine if the heads have been milled and how much they have been milled.

Good info, I'm stealing that tooling mark pic, thanks!