I think I have one of these 9400's. I took it off my truck because it lost adjustment nearly weekly, drove me nuts. I was a quick starter, though, even after sitting a few days or even when the weather was cold the engine would fire up immediately with a tap of the key.
Edit: The Carter was on a 305-307-350, I don't think it's a 350 because the engine is a dog, but it did lose adjustment quickly, and I don't know why unless they are prone to losing adjustment like that.
Somehow, this post eluded me, and I just read it.
No carburetor (even a Rochester B) if in reasonable condition, and properly adjusted, should need readjustment weekly!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
I bought my van used, with approximately 75k miles. I drove it for maybe 5k, and hated both power and fuel economy from the Holley. (Maybe if more of the fuel from a Holley actually went into the engine, they would get better fuel economy

). It took 5k (time) to get the Offy intake, Offy was backlogged even then.
I installed the Offy intake, and the 9400 at approximately 80k. It was UNTOUCHED until I removed it at 460k when the body rusted out for the third time from Missouri salty winters, and I scrapped the van.
Jon