Never use 5w30 in a tired engine.
Put in a new Wix filter. Change your oil to 20w50 Valvoline. Put in 2 cans of Restore for V8 engines. Take it out for a 1hr drive. Be sure to put 1/2 quart less 20w50 when you change it.
Park it next day you should have 30+ pressure. I had a 69 302 with Zero pressure, have a fresh 302 on the stand for it. Still driving it everyday, & I run the piss out of it.