Thanks Shay & Randy.
For more history on Falcon race cars this book includes a chapter on the Galaxies, Mustangs and Falcons that raced in the BTCC.
Alan Mann Racing took advantage of the FIA, suspecting they new little about the US built Falcons (and gambled they wouldn't attempt to verify) and had them homologated with fiberglass hood, fenders, bumpers and trunk lid. That made these lightweight Falcons 400 lbs(!) lighter than a Mustang and producing up to 400 HP these cars were rocket ships that dominated Touring Car racing for several years.