Try to find an older mechanic that has experience with your brand of carb and knows how to rebuild it properly.
skim heads. does not matter 2 or barrel carb
Currently the largest carburetor that Weber sells is the 55DCO SP. It has a retail price in the $450.00 range and is a two barrel side draft compatible carburetor.
No
That's typically caused by a worn "needle and seat" assembly. You can purchase a needle and seat assembly for a specific carburetor, but it's best to purchase a rebuild kit and do the whole thing.
I was looking at my Chilton's Auto Repair Manual and for a 1978 Mercury Cougar it only shows a two barrel carburetor for the 351 Windsor V8 engine
in cars, most of the time the carbs are two barrel which means there are two main terminals, if you want more power, you'd go with a four barrel carb witch has four main terminals.
In older cars 4v = a four barrel carburetor. 2v would be a two barrel and a 1v would be one barrel
I would say a 500 CFM but no bigger than a 600 CFM. I don't know if you are looking for an answer on flow (CFM) or just a generic answer like "two barrel" or "four barrel". As I recall, in 1963 the 283 was only offered with a two barrel carburetor. I believe the rated horsepower was 195. The carburetor was either a Rochester or a Carter. Flow was likely not more than 400CFM.
checker auto parts
In automotive terms, a 4 barrel carburetor that has two accelerator pumps, one for the primaries and another for the secondaries.
Companies like Transdapt make aluminum spacer-like adapters to mount a 2bbl carb on a 1bbl manifold . Not very efficient and they are application specific .
Remove the fuel line from the front of the carburetor by using a 5/8" wrench on the line fitting and a 1" wrench on the carburetor nut. Next remove the 1" nut from carburetor. There will be a spring and the filter. Note the placement and direction of filter, it has been awhile ,but it should be filter hole towards carburetor, spring, nut. There may or not be a rubber check valve in the new or old filter both styles work in will work. They only made two sizes of filter then a shorter one for two barrel carbs about an 1" and one but 2" for four barrel carbs.