I just finished my 454 build with that cam. Car pulls really hard. Has anyone ran that cam with a nos system at 100-200hp?Ive got 4:10 gears so it already revs quick.

If your car is already running 11:20's the nitrous may drop it about another half second at least, butI think the 4:10's will push the revs way past the reasonable level. You are right on the edge of a very unhappy motor.
Your plan of dropping the gears back(3.55-3.73) and going th400 is sound and will save on parts replacement.
Have fun.