All of the 348 carbs whether Rochester or Carter have the early rectangular bolt pattern (aka the Carter pattern). This pattern is 4 1/4 wide by 5 5/8 long.
The so-called "square" pattern was used from 1952~1956 (before the 348) and was 3 13/16 wide by 3 15/16 long.
A problem often arises within various carburetors of the "Carter" pattern in that the throttle bores were moved apart (from side to side) on center 1/4 inch on most units about 1961. Thus a 1962 carb, while it may bolt to a 1958 manifold, may experience throttle plates that will not open due to the center line change.
(Opinion) You will like your original (after you rebuild it) better than you will like the "clone", and for a longer period of time.
Jon.
