If I remember correctly the 5200 series were the ones that looked similar to the Weber downdrafts, and the 2300 series is the standard Holley 2bbl, looked like half of a 780cfm 4bbl
I,m sure there are apparent differences in how they function, the 5200 series is pretty much a clone of the Weber 32/36, probably a progressive throttle setup similar to the Weber with a smaller bolt pattern, where the 2300 series is both barrels at once, uses a larger bolt pattern, has external float adjustment, and uses most the same tuning components the larger 4bbl carbs use like shooter sizes, adjustable accelerator pump, and so on.
