450hp 340 oil pump suggestions ?

Honestly a stock pump is fine. It depends on a few factors not HP.
1) clearances- how loose is the motor? The looser it is, the more oil you need to fill those gaps.
2)rpm- are you dropping oil pressure the faster it spins. Most pumps “blow off” excess oil pressure out the by pass valve.
3)cost- as mentioned above, these prices are going higher and higher as child labor in Chy-na and delivery fees are increasing.
4) added power boosters like turbos need oil and that to me is where you need “extra” oil flow to compensate for the loss of oil flow/pressure.
Syleng1