For what engine to begin with?
Whats the purpose of upgrading an oil pump for?
If you are talking about RBs i reckon most people would run an aftermarket oil pump from Nismo, Tomei etc u name it.
As for SR20s, most ppl would run a SR16NEOVVL/ GTi-R oil pump.
Don't forget upgrading your oil pan to a bigger capacity oil plan which is also baffled.
For me if budget willing i will go dry sump (factory is wet sump).
Mazworx SR Dry Sump Kit - Engine - Mazworx
You can mount your engine lower for better CG,
oil starvation won't be an issue when racing where one would expect to encounter high Gs when braking, accelerating and taking corners.
And better cooling as you can carry so much engine oil.
If it's a road going car i will follow the principal of KISS. Keep it stock silly.
You want to get a faster car. Safe and invest the $ and upgrade to a better, newer and faster car.
Sorry to be blunt but the truth hurts....
There's no end to modding.