Yes, the AD Skyraider had seven major variants (AD-1 to AD-7) and a whole bunch of minor variants identified by various suffixes, for example the AD-4W and AD-5W AEW versions.
Curiously, in 1962 the DoD appears to have redesignated the seven variants still in service as A-1D to A-1J, so I'm not sure what A-1A/B/C had been originally intended for.