Priming a Flathead.

[Poncholover]

Is it easiest to to pull the dist & spin the oil pump (my usual method) or to pressurize the system by pulling an oil gallery plug?
This will not happen real soon but I am planning ahead.
Does that Distributor "stand" complicate things or would I just remove that to spin the pump?

[Bob Schuman]

To spin the oil pump you must remove the "tower shaft", the part below the distributor. The tower shaft is gear driven by the camshaft, and it drives the distributor and oil pump.
The alternative you suggest should also work if you have a source to push pressurized oil into the oil gallery.

[wheikkila]

The only problem with pressurizing the oil system is your not checking the oil pump to make sure it works. I have rebuilt a lot of engines over the years. And have run across two bad oil pumps. I know that the chances are low. but who wants to go back into the engine after it's been installed in the car. Now I run my engines before I install them. That wasn't always the case.
Thanks Wayne 

[Poncholover]

Bob's sage reply confirmed my suspicions, this method would allow me to clean things up & check them over first.
The current hitch is that the engine will not turn a full 360 so some exploration will be in order first.