What Carb for Poly Stroker

Bewy said
Look at the overall combo & remember what you built the engine for: predominantly street driving.

I could you build a great performing TQ that will tear your head off when the secs open...& give great economy. But I ain't going to Qld to dial it in for you.....

Your cam is mild-ish, only about 8* more 050 duration than the 340/275 hp cam. That is going to limit top end, getting pretty tired by 5000 rpm. So why put on a 6000 rpm carb on a 5000 rpm engine? Throttle response & mileage will suffer.

Holley's [ & clones ] are best left in the box they come in.....

The ideal carb for YOUR combo is the 625 AVS2. It will bolt on directly without an adapter. A 800 AVS will not fit without opening up the bores in the man...or using an adapter.
Your 600 H has 1 9/16" pri & sec bores. The 625 AVS has smaller primaries [ 1 7/16" ] for better throttle response & bigger secs [ 1 11/16" ] & has more total air flow. I have only heard good reports about the 625 AVS2. Edel changed the design of the AVS from the original Carter design which was a positive move in my opinion. They added venturies to the secondaries, originals did not have these.
I have been involved with the install of two Street Demon carbs. One worked well, one had a flat spot that was never able to be overcome, even with ph calls to Holley tech.

You're a really smart guy. But your constant bashing of Holley style carburetors makes you look pretty ignorant. Holley and holley style carburetors have won more races and are on more vehicles than probably all other types of four barrel carburetors combined. Why not just say something like "it's been my experience that blah blah blah......." and leave it at that. Even a novice knows how many Holley and Holley style carburetors are out there and knows they aren't "best left in the box they came in". That just sounds stupid. Just tell people something like "I've not had the best tunning success with Holleys" and leave it at that, because hundreds of millions of people around the world.....including IN YOUR OWN COUNTRY OF AUSTRALIA where the toilets flush backwards have.