The Carter carbs came on a good number of Ford cars with automatic transmission equipped 312’s in Texas. I have a stack of the carbs and still have an unmolested ’57 Club Coupe with a factory Carter equipped 312.
The Carter carbs as a general rule are more dirt resistant than the Holley carbs and therefore tend to make for better long term drivers especially if the engine sits for awhile between driving episodes. On the flip side, the Carter carbs can be finicky if sitting for more than just a few days in draining themselves of fuel which necessitates some heavy cranking or an electric fuel pump to get them restarted. The Holleys on the other hand like to be kitted every 2-3 years and can be tempermental at times when their air bleeds get a little dirty.
Thanks to NoShortcuts for posting the info from the YBM regarding the carb testing. From a performance standpoint and reproven on the dyno, the ECZ Holley 4V carb will outperform the ECZ Carter 4V carb when each are being run as delivered from the factory. But both are 1957 technology in fuel metering circuitry which has improved vastly since then. The newer carbs are more tunable along with better designed fuel curves which make them the better choice when camshafts, ignition, and compression ratios are altered from the original specifications.