Motor feels "stiff"

Definitely remove each spark plug and pour ~3 tsp motor oil in each cylinder. Not too much it could hydro-lock. Turn it over by hand with a wrench on the crank (1.25" socket I recall).

Most people prime by removing the distributor and gear and spin the oil pump with a hex rod and drill, but that is a pain and you risk getting your timing off and not priming at all if you spin the wrong way. Instead, I rigged up a little pump spray bottle (weed killer type $9.) and connect it at the oil pressure switch port. After a quart disappears from the bottle, I am sure there is oil in all the passages and bearings.