[Steve C.]

I certainly agree his engine internals will allow operation up towards 6000 rpm. That is setting aside his unknown valvespring specs that could leave the potential of the combo nosing over at rpm.
But I agree with the comments made here that his 'potential' peak power rpm certainly does not warrant shifting up in that realm.

As an example to support that, note the 5200 peak power rpm here in this combination below with a .050" duration cam. And NO, I'm certainly not suggesting it's apples-to-apples to the posters combo.
But I'll suggest it won't be a much higher rpm.

467 cid / 4.250" stroke
Unported KRE D-port heads
Crower hydraulic flat tappet cam #60919 w/1.65 rockers (0.517 lift)
Edelbrock RPM intake with Q-jet by Cliff Ruggles
Doug's headers



Here is the dyno sheet:https://pontiacstreetperformance.com/graphix/MikeG5.jpg

For conversation I would presume the KRE heads port volume is similar to the mild ported ported 6x-4 heads here in this thread. But probably not the airflow capability up through 0.600" lift as the KRE heads. While the roller cam here has the same .050" duration as the HFT cam it has more beneficial valve lift. And typical of a roller cam the power band, or operating rpm under which the engine is able to operate most efficiently, will increase from the 700 rpm as on the dyno sheet to 1000 rpm, or better. But his intake manifold and exhaust will certainly be a limiting factor.


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