Nozzle size for oversized pump

I bought a TSG-6835G Allison w/gearbox. I am running it off a Predator 420cc. Obviously I’m underpowered but need the volume more than the PSI. Is it realistic to expect 2300 psi @ 6.8 gpm? How do I know what size nozzles to buy? I think this would result in a 5.5 orifice size. Thank you for all your help