400 low buck dont give a

It's really tough to determine p/v clearance without having the engine in front of you...do you have something you can mock up to give you an idea of how much p/v clearance you would have? If you're still planning on cutting the heads down, I'd almost say you might wanna stay below .500" or so lift...but advancing/retarding the cam will have an effect on your clearance as well as the max lift. I'm new to big blocks too, so my knowledge of how much lift/duration you can get away with is very limited. I'd venture to say the best person to determine your p/v clearance is gonna be either you or the person/shop you request to build the engine...

...just my 2 cents...