Nathan - if ENOUGH time is spent on the B, it can get pretty close to the YF.
How much time is enough time ???
In 1995, I did such a test (no, no chassis dyno, no A/F tests, only "seat of the pants" testing on a Chevy Biscayne).
Now, the question is: "how much time is ENOUGH time" ???
The answer: 42 hours of shop time !!!!!
In rural Eldon, Missouri, the CHEAPEST shop time of which I am aware today is $60/hour, most are more than $100.
42 times $60 is $2520. Anyone want to buy a Rochester B for more than $2500 ??? If so, don't call me, today, I don't have 42 hours to waste on a B !
And the kicker is: in 5 years, you get to do about half of that again !!!!!
Jon