Do I need a hardened intermediate shaft for a HV oil pump?

Interesting above. Thinking logically, moving more volume at the same pressure requires more work and so more load will need to be on the pump's drive shaft, regardless of where that extra oil goes.

Just a thought: Perhaps your success with non-hardended shafts is because you rebuild and change things out pretty often.

Your excellent racing experience is great to hear. But oil starvation also depends on the duration of the high perssure/high flow situation. You could be approaching oil starvation 2x per lap, but never reach it due to letting off after a short time each time you rev it. I built an engine once with a high volume pump and a high pressure spring when I was younger, on an engine that had never had oil problems. I revved it I bet a thousand times for short durations to 6k-8k but then on the first very long duration high RPM situation, the oil overpumped to the heads and the engine starved from oil. So, short duration revs is not proof that oil starvation is not a possible problem on a given engine.