The 3646 Carter AFB carb is the primary (rear) carb for a 1963 or 1964 Buick dual quad set up. The main throttle rod has a "roller wheel" style that operates the transmission kick down switch. The 3925 Carter AFB carb is what was used on the 1965 and 1966 dual quad set up. It has a "attaching peg" style throttle rod for the transmission kickdown switch. FYI, the 3645 carb was the secondary (front) carb used from 1963 through 1966 for the Buick dual quad set ups.
What's it worth? Depending on the condition, I would think around the $150 range. Professionally rebuilt carbs would be about twice that. But like everything else in the secondary market, it's what a buyer and seller can agree upon.
John Egel
