Couple things...
You will need to or want to tweak the Edelbrocks to get to the 500HP level in a really streetable combination (I gues that depends on your definition of streetable though).
Intake valve size is not a problem beyond checking for piston to valve clearance. You could put a dinner plate in there. The exhaust is what gets close to the bore. A 2.19 or 2.200 valve is not going to "kill" the bottom end unless you go stupid big on the port. We're not building Boss 302s - where that story got started - with a huge port, a big valve, and a small displacement. Ford used the 2.09 valve 45 years ago in 428 engines that had warrantees, stock converter automatics and highway gears...
You can absolutely get a damn good running package with well worked 2.09, 3/8 stem, 30 degree seat stuff. But even Ford went to an 11/32 stem 45 degree valve in the "new" 1968 429. It's not like we're getting into risky territory here.
Any decent local shop can get you a nice gain by using the extra diameter to form a straightforward multi-angle 45 degree based valve job and bowl blend. A lighter valve with better flow, coupled with no real change in port cross section will get you an easily done strong package with no real downside.
The exhaust valve size can stay "as-is", but we normally go to the smaller guide there since people would think I'd gone insane with two stem diameters in the same head. A good valve job & bowl is all you need at that side for what you're doing.
You can fit a BT head in there - you'll be cursing but it'll go. I've had them on my car. But if you're worried about low end the current generation BT MR heads have a really large port and would be more suited to a big cube package.
Wes - that 416 had to be a pretty snappy bundle of parts to go 500HP with unmodified Edelbrock heads. Any info on that combo?
