They are rare, and my favorite 3 2bbls carbs for any sixpack set-up especially on the street. Less particular drivers can benefit from having the vacuum modulate the throttle position for them with the stockers, but I never liked the way the vacuum secondary stock six pack reacted while opening and closing. I prefer to control the opening and closing of the outboards directly myself. There's a disconnected response that I always felt was funky with the vacuum secondary carbs with a resultant lag time from pedal position to throttle blade position. The worst thing about them in my book is that noticable bit of lag time the outboards have in closing immediately after letting off the gas pedal.

Those look like they could use a quality rebuild, and the linkage and fuel lines are unusual. Another lesser known aspect of these carbs is that unlike their factory installed counterparts, the outboards don't have idle circuits in them. The motor idles exclusively off the center carb. This makes getting the A/F ratio set up significantly easier too. The outboards also use common Holley jets in a traditional metering block arrangement to adjust fuel flow.

Curious what you gave for the set-up, as they are no longer available from Holley, and quality examples have become quite expensive.

I currently have a fresh set to install on my 493" motor, and a second set being converted to use 3 of the large bore outboard sized carb bodies with the center carb being modified to have a functional idle circuit. The throttle bores are also being increased in size and having an aerosol booster installed in them. They should flow significantly more than the stock factory or Direct Connection set-ups. It should be interesting to see how much the power output is affected for better or for worse with the higher flowing modified versions.

I absolutely love the way these carbs feel under foot.