The timing mark on the timing cover looks like a tall skinny nose cast
into it.

I normally set my timing to about 20° BTDC on all of mine and it works
great. I DON'T disconnect the vacuum to do this because it affects the
idle speed too much - the 20° setting allows for the change made by
disconnecting the vacuum (if you have a vacuum advance/retard).
That way you don't have to reset the idle speed a couple times because
it is affected by disconnecting the vacuum.

BUT- if it runs better set somewhere else, by all means set it where
it runs the best!! It's your car, so set it the way you want it!
--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma