The engine builder I work with does a lot of 420+ inch SBC circle track engines and they typically see 20 to 30 hp increase from intake porting. The circle track guys tend to get their intakes ported but the drag race guys don't.

I'm thinking about getting the Trick Flow intake ported. I'd like to get that combo up over 700 hp also. I think the Quick Fuel 1050 carb is capable so it is just the intake that needs a little help.