By the 327 300 cam do you mean the gm 30-30 cam. Because that cam is not good for a blower motor. You may want to go with a nice roller setup for blower it will make ot pop off like you want. The large over lap cam will not snap like one setup for a blower.
You either want to run a efi cam or a cam made to work with a boosted application.
Look at the power output this way. If you have 14.7 psi of boost you will be adding another atmosphere to the engine. And in therory that should double the hp output of the engine. So back that down to 5 psi and you can guestamate how much power the engine will make. Subtracting for loss and the 25 to 50 hp needed to turn the super charger.