The Thermostat housing used by Cat should be the same as that sold on Burton Power.
The cap they say that is compatible is thier part number FC52.
Here is the compatability list:
Ford Capri Classic 1961-64
Ford Capri Mk1/Mk2/Mk3 1969-1987 including 2.8 & 3.0 V6
Ford Consul Classic 1961-63
Ford Corsair 1963-1970
Ford Cortina Mk1/Mk2 including Lotus Twin Cam 1962-1970
Ford Cortina Mk3/Mk4/Mk5 1970-1982
Ford Escort Mk1 1968-1974 including Twin Cam, RS1600, Mexico & RS2000
Ford Escort Mk2 1975-1980 including RS2000 & Mexico
Ford Escort Mk3 1980-1985
Ford Fiesta Mk2 1983-11/1985
Ford Granada Mk1 1972-1977
Ford Granada Mk2 1977-1985
Ford Orion Mk1 1983-1985
Ford Sierra 1982-11/1985
Ford Taunus 12M P4 1962-1966
Ford Taunus 12M P6 1966-1970
Ford Taunus 15M P6 1966-1970
Ford Taunus 17M P5 1964-1967
Ford Taunus 17M P7 1967-1971
Ford Transit Mk1 1965-1978
Ford Transit Mk2 1978-1985
Ford Transit Mk3 1986-1991
Ford Transit Mk4 1991-1994
https://www.burtonpower.com/radiator-cap-metal-type-fc52.html