I love the 4-barrel and headers on my Ugly Truck. I agree with Arpee about the 4-barrel being less of a hassle to adjust than dual 2-barrels. I'm running a Carter 625, which is essentially the same thing as an Edelbrock 1406 (600 CFM.) They're real easy to adjust and once set up hardly ever need tweeking.
My gut feeling is that the stock exhaust manifold is WAY too restrictive. I'm basing that on the sound of the exhaust with the stock manifold and a straight pipe vs. the headers. With the stock manifold, I couldn't tell that it WAS a straight pipe. But with the headers, there was no doubt. I had to add mufflers.
My website url is in my sig.
There's info there on the carb/exhaust installation. a rule of thumb that works for me is, "would I do it again if I had it to do over?" the answer for me is "absolutely. In a heartbeat."
