A good set of GRP rods is a little over $1,000. If your budget cant handle that you have no business running more than 125hp of nitrous. You can bet the farm that long before you get close to a 500 shot you will have hurt a set or two of pistons, rockers arms, push rods or some other motor repair. And that doesnt include axle, gear or transmission breakage along the way.
Most people that claim they are running a 400 or 500 shot are full of BS.
400+ of nitrous is a lot. I run excess of 800hp of nitrous on top of 1,000+ hp motor. How many sets of burnt pistons do you want to buy! Lol.