I have

 

there is not enough info what type of rods, crank and pistons i have a 6.0 408 with lunati pro billet rods lunati crank custom dimond pistons and a 300 shot on mine wouldnt be a prob i have'nt tested that one though 150 was the most on mine but i KONW mine will handle a 300shpt

 

i have

 

i would say that you shouldnt have a problem with a 250 shot what kind of crank?? make sure you have enough fuel you can have a fully built motor and not have enough fuel and still break something i would check with your engine builder on how much nitrous the car was built to handle. when i had my motor built i had it built to handle a 300 shot but i am sure 50hp extra wouldnt hurt a thing see what i am saying??

 

I have been running a 250 shot on my 6.0 and have ran about 10 bottles through it. This is with stock internals and 120k on the motor.