Here are a couple of ideas for you to consider, I have used them in the past.
First, pull the bottom spark plugs out, and put them aside for a while.
Pull off the oil line that goes to the firewall mounted sender.
Now, pull the prop through slowly----you are looking for binding or rough places. It should pull through the entire 360* pretty smoothly. Make only one or two turns to check for binding etc.
If all feels correct, then you can either continue hand spinning the prop until oil runs out the disconnected line, or if you have a really good battery, hit the starter and spin the engine till oil comes out.
Now, go inspect everything you can see on the engine. Look for anything that might be amiss------oil leaks are top of the list. Look for, and wipe up any preservative oil that has been forced out of the bottom plug holes.
Once you are satisfied that all is well, reinstall the spark plugs--make sure they are not oil soaked from sitting with preservative in engine, hook the oil pressure line back up, and light the fire
......Cowling is off, by the way.
Have a couple of folks standing by with fire extinguishers if you can, have these folks looking at the engine as it starts---watch for
anything that seems wrong, loose parts, leaks, ??? Make sure you have signals for immediate shut down if something is wrong.
After a minute or so, shut the engine off, and give it another look over,-------and fix anything you find wrong. Dont worry about trying to cycle the prop, fiddle with the mixture -----rich only---- or check RPM range. Just let it run 1000--1200 RPM or so, should smooth out and purr.
By the way, oil pressure should come up in seconds with this method, if not shut it off and find out what is wrong.
In this first run, oil pressure is number one concern, temps, volts/amps etc are not something to worry too much about.
I am sure others will chime in with more, but this should be a good start for you-----and your engine
