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I have a Quick Fuel HR-780 vacuum secondary's on the 351C in my truck. Had to recalibrate the idle circuit and change out the accelerator pump cam. Other than that it was pretty close out of the box. They are completely tunable.
Holley seems to buy up all of it's competitors. Then there not quite so good as they were. i.e. Speed Demon used to have actual brass jets in the metering block, not the main jets. Now they are just drilled holes in the aluminum.
About a year ago I had a customer bring in a Brawler carburetor to run on his 358 inch Chevy. It ran fine on the dyno and the engine made 600 horsepower. It came with billet blocks, base etc that were fair quality. Would it compete with my 950 HP that was built by Competition Carburetion? Absolutely not but it was ok.