Massive oil leaks.

I'm relatively new here and not as polished on big blocks, with that being said I will share my personal experience. I built a 340 that had 90lbs of oil pressure at idle and all was great for 30 minutes and then oil began dripping until a full stream appeared underneath the car. I inspected everything and replaced the rear main seal. I still had the leak. I repeated this for 3 main seals and rear bearing inspections. It turned out to be the plug at the rear of the camshaft. I had used one of the brass freeze plug kits and used the plug that came with them. The leak was pouring out and down the block and appearing to be a rear main seal leaking. I found it by being under the car with it running and a super bright light. The camshaft bumped the plug just enough to loosen it. I replaced it with a mopar camshaft plug that is made differently to prevent this and all was well. I had a massive oil leak however that made a mess everywhere. Not sure of the plug on big blocks but hope this gives you another area to look at.