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I'm wondering if the clearance was too little with heat and if that could cause an oil pressure drop

Hi Frank, Read your line again. Can't happen.
More than likely it would be a stuck relief valve.

Cheers, Charlie
If It ain't broke, Modify it!
87 Montero turbo Converted back in Spring1989
95 Montero SR 3.8 DOHC Only one?
93 Pajero 3 door 6G75 Mivec with paddle shifted 5 speed
Then a Gen2 SR with full coil independent suspension.