holley 800 cfm

That does sound like a pretty big cam but if it's not running right it may pull some more vacuum when you finally get it tuned in so I'd go with a 3.5 PV to start.

I've heard of guys drilling the primary plates to get more air in. Even read it in a Holley book but I tried it on my 750 and it didn't work out good. It idled fine but then ran rich off idle. I replaced the primary plates with new ones and opened the secondary idle stop adjustment a half turn and re-adjusted the idle mixture with the trans. in gear and parking brake set and it ran great all the way through the range. Vacuum now runs about 7 to 7-1/2 inches at idle. (pretty big cam in mine too).

I agree with 6pkmopar about the carb being too big. And being a double pumper with a tight converter like you have will probably make it pretty hard to tune. A 750 vacuum sec. in my opinion will work alot better for your application. I'm running one on my car and have a fairly large cam so I have the 3.5 pv in it and one size bigger jets than it came with and it runs great.

A buddy of mine bought a new Holley 4150 HP series 750 double pumper and he let me try it on my car just to see how it would run and it bogged bad when I mashed the loud pedal real fast and I had a 2800 converter and 4:11 gears. I even went up one size in the jets all the way around and it still bogged pretty bad and then it ran a little rich on the top end. I'm sure I could've tuned it better but since it wasn't mine I didn't worry about it. I doubt it would have ran better than the 750 vac. secondary but that's JMHO.