740's are plenty. Good rule of thumb for a 3L 6 cylinder motor is the cc of the injector will flow that much crank HP. so if your motor is making 550wheel hp(not rearwheel) then 740's are still enough. Now you start making numbers like 750, 800ish hp, you are border line. both are good injectors, its the same to work with on both setups, one is just alittle more advanced and will flow the fuel better for more advanced setups