To add to Jerry's comment above:
The biggest hurdle in adding a Q-jet to a 283 is finding an intake manifold.
DO NOT EVER
USE A SPREAD-BORE TO SQUARE-BORE ADAPTER PLATE (think NASCAR restrictor engines)
Up to and including 1974, virtually all Q-Jets were 750 CFM, a few were 800 CFM, and a very tiny few were 850 CFM (and currently worth a small fortune!).
But, as Jerry mentioned, the Q-Jet is an air-valve carburetor, so read the CFM as follows:
750 is 150 fixed plus 600 variable
800 is 200 fixed plus 600 variable
850 is 250 fixed plus 600 variable
And as Jerry said, some were equipped with a restrictor bracket on the air valve to reduce??? performance to comply with the GM equation for horsepower versus weight (exception - Corvettes).
The smaller Rochester 4G series carbs were about 350 CFM (read as 175 + 175) And 175 is pretty close to 150 or 200
By 1955, the 4G was an excellent carburetor, and while the Q-Jet is somewhat more technologically advanced, the 4G is more reliable. The 1952~1954 4G's are best left to the numbers matching folks.If you are running a basically stock 283, you will gain no "seat of the pants" performance increase by going to a Q-Jet; although a dynamometer MIGHT measure a tiny increase.
Two considerations when rebuilding a 4G carburetor:
(1) read the GM / Rochester bulletin on adding a bushing in the vacuum circuit to an airhorn mounted automatic choke, and add it if it has not already been added.
(2) Rochester (like Carter) used DIFFERENT FLOATS THAT LOOK IDENTICAL UNLESS ONE KNOWS WHAT TO LOOK FOR! As it was determined that on some units the primary fuel bowl should have a higher fuel level than the secondary bowl, the different floats were used. The difference is in the height of the pontoon where the arm is attached to the pontoon. The same arms and same pontoons were used, just soldered at a different height. DO NOT MIX THEM!
The different floats were necessary as the maximum force created by the buoyancy of the float transferred to the valve occurs when the float arm is perpendicular to the valve.
There are more vendors supplying Q-Jet parts, but, with the exception of SOME of the 19 different floats used in the 4G, ALL calibration parts for the 4-G are available mail order.
Unless drag racing with a really modified engine, I would personally not make the change (and the Q-Jet is one of my top three 4-barrels).