Tom, it is a turbonetics 78mm BB. I'm not real sure if it will change the rpm range that much. Our nitrous motor made all the in the 5000-6600 rpm range. We kept the turbo kind of mid size to make it spool easy. It would have be cool to put a 88mm on there. We think you are reaching the outer limits of the durabilty of the comobnation.
We decided to limit our combonation 1000-1100hp because that is where the fuel pump, intercooler and some other componets are rated to. Heck, 8.60-8.80s @ 150mph in a 70yr old truck is fast enough for me