How about a clutch type SC, intercooled while you're at it. The intercooler will only work while you're getting plenty of air on it and it won't matter anyway if they don't engage the super. This should keep you from acheiving ANY boost on the dyno, yet allow you to run as much as you want on the track or street without having to swap parts. Perhaps you could disguise the boost switch as a trunk button or something so they won't figure it out. I know such a type of supercharger exists since there was one on the SVT
Super Stallion, found here: http://bradbarnett.net/mustangs/concept/superstallion . Perhaps you could search around and find something similar for your application, or maybe engineer one somehow. On the other hand, if you're going to run a LOT of boost, you'll have to lower your compression which will decrease power below stock with no boost, in which case you should just change pulleys as has been suggested before. Hope I could be of some assistance, good luck.