360la loosing oil pressure at high rpm.

I installed some roller tipped rocker arms and now when I hold a high RPM you can watch the oil pressure drop. I am using a magnum stock pan as I wanted the one piece pan gasket. I can't seem to find a 8qt pan for the magnum... ?

I think that since the oiling on the rockers is better , I just run out of oil in the pan.

Anyone else have these problems? Is there an 8qt magnum pan or do I have to go back to the LA pan without a one piece gasket?