I have a double pumper holley with a MrGasket dual feed line, on this line is a 1/8" npt fitting, can i tap off that for a nitrous fuel feed?
it's a red holley electric pump, i'd figure maybe a 125 shot
they have 1/8" to AN4 fittings, which would work for the fuel supply right?

i figured at most with a 125 shot that would make 400hp

rpm range i am aiming at it 3-5.5k range

the red pump should be enough for the motor and nitrous right?

i'm looking into the NOS super power shot kit or one of the edelbrock kits

 

You would be better off buying another pump and running a dedicated line fuel side for the nitrous systsem.If you go with a holley style atlleast get a blue.
The way you are looking to run it there is not enough fuel supply from that pump to supply the motor and nitrous.
Dave