I dont think you can go wrong with anything around the GT35 range (either a GT3540 or something slightly smaller, GT3240), they will easily give you the power you want (rated around 600-700HP) and beyond and being a 3L this gives you the displacement to spool it up quickly.
Quick edit: Just noticed you have 500cc injectors, are they actually 500cc or nismo 555cc injectors? Either way, if you want to go much over 300, say 330ish, id probably recommend 740cc injectors just so you arent running the 500cc on such a high duty cycle.