2 circuit
Guys, correct me if I am wrong.
Originally the annular discharge, 3 circuit dominator like 9375 was designed as a tunnel ram 2X4 carb combination. 3rd circuit was to help cover up the flat spot on a tunnel ram with their big plenum volumes.
Then someone,(anybody know who?), found out the annular discharge boosters were better for some single 4 applications and the 3rd circuit just came along for the ride. Now all Dominators are Annular discharge but you get the choice of 2 or 3 circuit.
Don't really need the 3rd circuit on any BBC unless tunnel ram? Maybe still needed on SBC?