you can run nitrous any any motor with or without mods. go to ebay and search motorcycle nitrous kits and thats what you gonna want.
It depends on how much fuel you have to compensate, not CR ratio. Personally I think its a cheap cop out, make as many ponies as you can with motor mods then spray it, this is when your gonna see the most benefit anyways. Plus its hard on internals, JMO.13.5 is a little high for spray though if im not mistaken[/b]