[Tom Vaught]

Good Morning.
The first Picture (Picture #26) is an old Holley Carburetor Magazine Ad showing the 3 Carbs designed for Performance in the 60s. The #4224 Holley Center Squirter, the Holley 3-BBL (Vacuum Secondary) carb, and the 350 & 500 CFM 2-BBL carbs: #7448 & #4412.
That series of Carbs has had a long history of Racing Success in many different types of competition.

Picture # 27 (sorry for the typo above), shows all of the drillings on the secondary side of the typical Vacuum Secondary (metering plate) carburetor.
The Threaded Holes attach the Metering Plate to the mainbody and the plain drilled holes are the Fuel and Air passages for the carbs operation. The spots with the black marks next to them are the Alignment/Attachment Holes.

Picture # 28 is your typical Dominator Replacement Fuel Bowl Set.
This allows you to put the fuel into either side of the fuel bowl.
It also allows you to have new bowls if you have a good used mainbody and metering blocks.
The kits can be had with the "Sight Plugs", the Bowl Screw Washers, the Bowl Gaskets etc. The accelerator Pump, the Fuel Nuts (to block the opposite side opening, and the other parts like the Needles and Seats are all extra cost items in the catalog.

Tom V.

The #4224 carbs are still out there.
I have a few of the old #3160 carbs (3-BBL) in 950 and 1050 cfm (4 bbl ratings) but the parts for them are long gone.

The Old #4412 500 cfm 2-bbls are common, the old #6425 (650 cfm) 2-bbl circle track carb and the #4782 and #4782 Mechanical Secondary 2-bbl race carbs are occasionally seen on e*ay.