I have seen some "tricks" by the older engine builders from the 60's-70's. They are the ones with 5/8" holes between the mains and cam bearings with Holley jets threaded into them....or hogged out passages from the pump, etc. There were a lot of things that they tried back then, but they have since been proven as wasteful or downright wrong.
There are no inline valve FE heads that flow 400's....BBM included. I've been working on a set of BBM's for a personal project that are flowing around 340-350. Keith Craft's Stage 3 Edelbrocks hit around 380, but that's the most I've seen. I used a set on Mr. Brown's 496. I've also got a set of hand ported Tunnel Port heads here that flow in the 370's. Most of the "good" aftermarket heads have the heart shaped chambers as you say.
If you're ever willing to give it a shot, a hot
oil pressure at WOT in some of my race stuff is about 75-80 psi. Main bearing clearances are usually around .0017-.0018 on aluminum blocks, a little tighter if I use coated bearings. Rod bearings are usually around the .0025" mark with BBC rods. Of course I measure my cranks and have them ground if they're out of round or tapered by any more than a few tenths. Just remember that high
oil pressure costs horsepower and causes heat. Where do you draw the line? If 100-120 is good, is 150 ok too?
Stay warm man, I think we're all gonna get dumped on. Tomorrow is high 15.....