The oil leaves the pump, and goes to the three full-length oil passages from back to front. The ones on the sides supply the lifters, and the one in the center lubes the cam bearings, then the main and rod bearings. 55's had a BAD habit of wearing out the cam bearings to the point that the oil pressure would drop below 7 PSI at idle and make the idiot light flicker. The main and rod berarings got starved for oil because of massive leakage at the cam bearings. The only good fix is to do a total rebuild, including new cam, rod and main bearings. You can do a temporary fix by running a Melling high-volume pump to offset the cam bearing leaks with higher oil volume.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!