This is not going to end well. That noise you hear could be wiping the cam lobes off. At this point it appears the engine has to come apart. We installed a 'Nascar built' Cleveland the Pantera customer provided this year. NO oil up top. NONE after 20 seconds. Nascar nothing. It was put together in a shed somewhere. Pulling the pan, the oil pump was hanging on one bolt. An oil galley plug was MIA.
Yes you are correct our oil pressure like yours was 70 psi at the time. Means nothing if the oil isn't getting up top. Oil is fed to the cam bearings and main bearings from the front of the block, lifters are last. Don't run it any more. Put a dial indicator on and measure lift across the board but again, don't run the engine. It's not going to self correct.