Thread on the studs for a 66 clock

[DatsunNoob]

I need to learn the thread size for the hold down studs on a '66 clock. I have only 1 wing nut and I thought it was a 6-32 but that's too small and a 8-32 is too big. I don't have any small metric taps.
Any body have any idea? thanks

[ADR]

My 66 clock was just restored by Jon Frampton. Waiting for install. It's 100% certainly 8-32. The near-fit metric has a thread pitch that is too fine.

Besides, the 66 is full SAE. No metric other than sins of the prior owner!