What are peoples thoughts on this ?

I am getting some oil pressure fluctuation just before finish line then some drop when backing off .
Normally run 60-65psi wide open , is fluctuating down to 50/55ish then back up to 65 then drops to 30/35 when i lift . Comes back up after about a second or so to 45 . RPM is slowing through 4500 at this time .
Motor is a Mopar big block , 505ci . It is a World iron block , Mellings HV oil pump , solid flat tappet cam . It has a Milodon road race oil pan with 8 1/2 quarts oil , Penn Grade 20/50 currently . Will be going to Royal Purple 20/50 . New motor has about 20 passes and 6-800 street miles . Vehicle is my daily driver , bracket race monthly .
Oil pressure cold is 70psi , hot is 18-20 psi in gear idleing jumps to 40psi from idle to 3500 then up around 65psi . I do not have any issues in daily street/ highway running

Thinking whether I go to an Accusump . With manual valve so as only operating on race day . 45 or 55psi switch ? Sandwich adapter at oil filter.
Try an extra quart of oil ?
Not much room in the engine bay , 68 Satellite . .

Tex