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Did you restrict oil to the cam journals? If so did you do it by drilling a smaller hole in the cam bearings?
Did you block the passage at the front of block going up to the driver side galley.?
Lifter bores, cam bearings, rocker gear are huge internal leaks that the system can tolerate at 3000 or less in a street car. Everything was done to control all that oil, supply just what was needed, where it was needed, and keep the rest on the crank. Everything was done for use with solid lifters, either rollers or flat. Hydraulics would need a different approach, but hydraulics would probably not be used if the engine was expected to go 7500+.
Lifter bores were bushed. Just a nicer solution than the tubes. "Crossover" was not used. The oil to the left galley was blocked at the main bore and left dry. There are other ways to do it. That galley only lubes the lifters. Not needed with a solid cam. Cam bearings were left alone. Oil to the cam bearings was restricted way down at the main bore.