70 Nova,
Reality check here. If you have around $8-10,000 to spend then you can look at that kind of HP. More down to earth would be 350-400 depending on what HP the engine is already and the existing compression ratio.
I would recommend getting a Demon carb. They have a record of pulling more HP with the same or smaller CFM rating and better fuel ecomomy.
Check with the tech dept of Comp Cams and tell them what you have. They can make recommendations on the best cam for your application with out hurting HP. A cam can be too big.
One more thing. Think about drivability. An engine with 600-650 HP will not be very streetable, and won't run on pump gas.
Ed