SB engine rebuilding got ya! School is Open!

Make sure the oil slinger is in it, and pointed correctly, along with the big felt seal some people just toss to the side. You can't believe the leaks you can get. Acetone, xylene, mek. Old sillycone residue is hard to get off, it may look clean, but feel it....

Problem areas; rear main, clean (use permatex right stuff in problem areas), make sure the seals aren't flush with the cap, rotate both 1/4" into the cap and block; timing cover/oil pan, sealant; front and rear of intake-toss the cork, use big bead of right stuff(not into the valley). Right stuff on front and rear exhaust studs.

Get a Harbor FR infra temp gun, check each exhaust tube on brek-in; stop if it shows carb is lean; rich is better, lean raises the temp. Degree the cam twice. B#tch to take front apart again. prime, then spin it over until lifters pumped up. No retarded timing, hot.

Coppercoat head gaskets, We all have different ways, but what everyone has said so far, I completely agree.