Question about Carter 2bbl carb numbers

[1968 Dart 270]

What is the difference if any between a Carter 2bbl 4417s (1968 273 v8 at) and a 4421s (1968 318 v8 at) and a 4608s (1969 318 v8 at) they all appear to be physically exactly the same. I'm just curious if functionally there is a difference between the 4417s which is for a 273v8 and the others that are for 318 engines

 

[krazykuda]

It is most likely the calibration... Different size jets and squirters....

They all will work on your engine...

 

[1968 Dart 270]

Figured that was likely the case. I was just curious.

 

[cudamark]

The step-up rods and the float needle and seat are different, probably jets.....maybe other things as well.