Bigblock,
Because I know how much DI and Argentina know I am embarassed to step in again, but fools' names and fools' faces are often seen in public places, as my mother used to say.
IMHO a bigger or lesser carburetor cfm, strictly speaking, isn't the root of an off idle bog. Rob (DI) and Argentina on this forum explained the basics (on this forum) of bog creation and it starts with YOUR engine. It seems as if nearly every slant is different, plus the platforms they are in and the feet stomping the gas differ. Still, if you look at Argentina's thread with lots of pics (he called it "not dialup friendly", look at cstryker's exploration of the reverse idle carb, and look at Rob's listing of parts he uses and has used, you can see something explored really well in Mike Urich's Holley book..That is, .the idle transfer slot "wetnes" in relation to the inches of vacuum in relation to which power valve you use, matched to jets, can remove or put in bog on ANY Holley.
For instance, My 4180 upgraded to 4150 following Rob's advice on springs and metering block was too rich with my selection of 10.5 power valve and 57 and 62 jets, but NO bog at all. In a heavy truck with a RV cam and a 3.91 and 4 speed.
I did the cardinal sin and changed TWO things at once, down to a 6.5 power valve and 47 jets. No bog at all, because engine would not even idle below 2,000 rpm and would barley crank without an ether shot! Had melted tires and run fabulous on the 10.5 and 57...So, I changed back to 50 jets and an 8.5 power valve. Runs fabulous, no bog, starts without really turning over.
It has to do with vacuum under primary plate and how much you have to expose the idle transfer slot to idle appropriately. Open plates up, initiate fuel flow in transfer slot, rich, = no bog. BUT, you have to set the idle speed screw underneath the carb base to spec, which is .025 (IIRC) between the throat and plate, and primary and secondary plates need to expose the same amount of transfer slot at that time.
My plugs read perfect now and I know I still can tune better, but I think I have wasted enough words here when others know tons more. DON'T jump on the 600 bandwagon just yet. I feel as if I want some cfm between the 390 I have now and the 500 I had with the Eddy, but below 75 mph I can't see a time difference in my truck and haven't had a chance to go faster. I am built for torque and life below 4,500 and it may be that those who want to live from 4,000 to 6,500 are gonna need more short term cfm, just like sprinters vs. marathoners.
But remember, I am just a beginner and am also still searching for the perfect recurve. I am close now on my curve, but changing jets, heads, and PV has changed my advance needs, I think. I am gonna find out by testing, and writing it down.
Regards to everyone,
rock
'64d100
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I'll be driving this thing everyday.
I understood alot more that time.....it took a while to get through. Sorry guys. 
That's what is so great about this forum....people 