Head Clearance Measuring Tools?
I might be dating myself here. The traditional North American brands would be "Starret" or "Brown and Sharp". Of equal quality but made in Japan is "Mitutoyo"
It has been some years since I purchased these tools, they last for ever. I have only a Mitutoyo catalogue.
A suitable micrometer would be a Mitutoyo Cat# 202-101
A suitable depth micrometer would be " Cat# 129-147
There are other lesser brands around. You get what you pay for.
Ed S