My take on the oiling system crossover tube for the small block

We can't automatically make this conclusion on the pressure drop; you gotta account for the possibility that the 2 separate gauges are reading differently; the one at the 'line psi' location just may be off.

Some SMALL drop at the normal oil pressure sensor point ('line psi' in the data) with RPM is to be expected. Once the pressure relief spring starts limiting the pump outlet pressure, then the pressure at the top of the passages into the passenger side gallery is subject to the flow through the engine; that flow gradually increases with RPM, and will drop the pressures into the gallery a bit due to flow resistance in the filter and the passages to/from the filter. The 'line psi' difference 3k to 6k RPM is -2 psi; seems pretty good to me.

OP, what filter are you using?

From the data for 'oil psi', it is pretty obvious that you have the 50-ish psi relief spring with the present HV pump. So if the new pump is shimmed up to around 70 psi, then you ought to see a big change.

I 'took a look' yesterday at that site.. it did not say anything to help understand this.
I agree with what you are saying but imho he should verify that he has 50 psi at 6,000 rpm and not 36. I think the line pressure reading dropping at higher rpm is indicative of an excessive leak.
The other reading stays steady at 49 psi regardless of rpm but the line pressure reading even with a bum gauge drops as the rpm goes up. That does not look right to me imho unless you have oil gushing out somewhere like lifters.