I wouldn't trust the stock mechanical pump to keep up with both the needs of the carb and the spray at high demand. I don't know enough about the Holley mechanical to comment. I don't know what kind of demands it can meet. Myself, I would run a Holley electric with regulator and pressure gauge, or some other good brand just to feed the N2O and feed the motor with the Holley mechanical. Some might say its overkill but I know when I hit the button and stretch it out through the quarter I'm not going to run out of fuel, or have nitrous related engine damage. I always flow my plate over a bucket to set fuel pressure also. 6 psi with only the fuel solenoid connected and activated, flowing fuel through the plate. I'm assuming you have cast pistons, definitely not as forgiving as forged also. Do it right and don't be afraid to use it or don't do it at all. Nitrous systems are not just bolt on and go, you might get lucky until you don't. Just my opinion.