B - 27.6 is ideal
I have a D(41.1) in my 36 Coupe 221cu with 3:78 rear end … really nice on the highway . Also have C(37.9) in a 31 Model A also 3:78 rear end.
Sorry for the bad resolution… so with the clutch disc and PP fastened to the flywheel, measure from the top surface of the PP down to the finger surface/adjuster. Your looking for the following:
9” disc should be 11/16 ( disc is .340 thick)
10” disc should be 15/16 ( disc is .295 thick)
11”...
Check the thickness of the clutch disc. Most of the new discs are slightly thinner than the original. That coupled with an improperly surfaced flywheel and the PP not adjusted could can cause the clutch to slip/chatter.
Here is a good article that explains the circuits in a carburetor. The Idle circuit including the mixture screws is explained very well… even though the focus is 4barrels, the theory is the same.
https://www.hemmings.com/stories/article/the-lost-art-of-2