Heres my take.
I'll assume you also went with 13:1 compression when you went to the 1397. I'll also assume yopur cam timing does not close the intake vale to early, let just say your cam timing is around 105 / 107. I'll also assume you are running the NOS through your air filter. Then you should be able to run a 50 shot with no issues, but here are some very important points to consider.
#1 - Make sure you know what your boottle preasure is...Invest in a bottle preasure gauge because you should be running around 900 PSI, but I have seen bottles in Florida jump to over 2000 PSI in the heat. That might make your 50 shot make your motor go BANG.
#2 - I probably would not start spraying until late 2nd gear or early 3rd gear......
#3 - Buy an air shifter.