[Pibwl]

028 M8 Greyhound could never carry that much ammo (32 HE, 80 AP). According to Osprey NV 053 M8 Greyhound, a factory stowage was 80 rounds. In fact, cavalry cars had two radios in a hull, what caused a reduction of ammo to sole 16 rounds in a turret. Such cars were manufactured from 3/44 (or maybe even modified from 11/43, when two radios were authorized?). After applying different field modifications (eg. 16+36 rounds), a field modification with 79 rounds was accepted in July 44 (43+20+16). Cars from tank destroyer units had original 80 rounds.
BTW, the gun was M6.