 Firth and Reaburn also teamed in the 1965 Armstrong 500, but while the winning Ford Works car of Barry Seton and Midge Bosworth was the Harry Firth developed Ford Cortina GT500, Firth and Reaburn finished only 14th outright but won Class A for cars priced under £920 in a Mk.I Ford Cortina 220.As part of his work with Ford Australia, Firth was recommended as a driver by a young Canadian born Aussie racing in the new Trans-Am series in the United States named Allan Moffat, and he traveled to the US and co-drove with Moffat in an Under-2 litre class Lotus Cortina in two races, a six-hour race at the Green Valley Raceway in Smithfield, Texas, and a four-hour race at Riverside in California.Following the Riverside race, the American's reportedly wanted Firth to stay and help the team but Firth refused, stating that he had to be back in Australia for a rally.