How often do you do them?
Do you want a valve hanging down as the lowest point of the car?
I don't know the thread for that pan, but seems I read it was 1/2-20, but I could be wrong. Could be metric. I'd be inclined to take the clean pan to about any hardware store or automotive parts store and use their thread gauge to be sure. I do know that I used that thread for my self installs.
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Problems huh? Then Read THE Book. Signed: Natural Borne Neanderthal .