Ron,
The 351C was produced in the US from mid 1969 to mid 1974. They were exported to Australia from 1970 to 1974. Australia began domestic production of the 351C in 1972, but US imports continued flowing into Australia through 1974.
All 351C's produced in Australia had small port heads, including those equipped with 4 barrel carburetors (Australia does not use the 2V - 4V nomenclature). However, after US production ceased in 1974, a significant number of surplus US motors were left over as new old stock in Australia. The relationship between deTomaso & US Ford was bad after the split, which occured I believe in September 1973. When deTomaso resumed production of Panteras after Ford shut down the Fossalta factory, they sourced the 351C from Ford of Australia. The earliest motors sourced from Australia were actually surplus US manufactured 4V motors, but when that supply of US made 4V motors dried up, they resorted to purchasing Australian made 351C motors, which all had the small port (2V) - open chamber style heads.
Australia ceased production of the 351C in 1982, between 1983 and 1989 the 351C's installed in Panteras were surplus, new old stock motors from Australia.
The last several Panteras produced in 1989, before production of the Pantera Si began, were equipped with 351W motors sourced from US Ford. DeTomaso had re-established relations with US Ford, had made arrangements to use a fuel injected 5 liter V8 in the Si, and even had plans to import the Pantera Si to the US.
Ron (accobra) owns a mid '70s GTS with an Austalian sourced American 4V motor.
your friend on the DTBB