[Healeys] oil galley plug?

[Jerry Costanzo]

On the carb side of the engine, there is an oil galley just above the engine
mounts.  At the front of the engine, there is a hole that I assume is filled
with a bolt or plug.  I can't seem to find what the threads are for that hole.
I thought was 1/8 pipe theads but I just bought a plug at ACE hardware and it
does not fit.  Looks like it must be tapered?
Any help.

Jerry
BJ8 engine