Carb size ?

Here's the thing about Holley carburetors. If I were going to run one on a mild slant, it would be a simple, cheap single line 600. Since they are a vacuum secondary carburetor, they are only as big as the engine demands. Real simple to tune the primaries down if they are too rich. The 390 is essentially a tunnel ram carburetor and designed to be used in pairs. A stock super six carburetor probably comes close, so the 390 is really not very much of an upgrade, plus, it's very expensive. Can they run well? Sure. I just wouldn't recommend one to a newbie for a slant, because a 600 will do the job far cheaper and have more on tap for when you upgrade the slant later on. You can find a 600 at a swap meet for 20 bucks and a kit for about the same, build it yourself and you have a cheap carburetor that will out perform a 390 any day of the week, but be mild enough tuned down to run on a stock slant. It's not that I have anything against the 390. They're good carburetors. But even a mild slant with dual exhaust will flow more than a 390 can deliver at high RPM. To me the 600 OR the smaller Carter is just a no brainer. Another choice although not a 4 barrel is the Holley 2300 500 CFM 2 barrel.