In looking at your original picture I see an additional linkage rod associated with your stock linkage which is non-standard for SBF linkage. Firewall to carburetor linkage is on the driver's side and not the passenger side unless you are running a set of FE 6V linkage?
Is that the case in this...
On all Ford SBF 6V carburetors, only the center carburetor provides idling while the outboards are adjusted so that a slight amount of air passes into the carburetor but not enough for either the outboard carburetors to take over idle or conflict with the center carburetor. The center Holley is...
On Ford Holley 6V carburetors you will have an official Ford Part number and the Holley List number. SBF List 2667/2668 260 (730CFM), List 2881/2882 289 (675CFM), List 2436/2437 FE (1030CFM), List 2497/2498/2499 FE (1030CFM) and List 3208/3208/3208 FE (860CFM)
Both SBF and FE 6V Linkage(GM language is Tripower) is nearly the same. Specifically the two individual shafts which fit between the center carburetor and each outboard carburetors are identical and are adjusted exactly identical whether a SBF or FE.
When laid out next to each other many people...