When it was launched in 1955, the beautiful MGA ushered in a new era of modernity at Abingdon – out went the pre-war cycle wings of the T-series car, and in came a slippery new body with Le Mans inspired styling. The MGA made liberal use of the BMC parts bin, with its B-series power unit coming straight from the Morris Oxford. Performance was hardly sparkling, but quick enough to impress the Americans, who bought the MGA in their container loads. For those who wanted more performance, the Twin Cam that followed was just the ticket.
info from Octane