One new original Lucas 14TR alternator voltage regulator (made in England), part number 37596, UCB105, UCB104, UCB109, 37648.  This is a four wire unit (red,black, yellow & white).  This fits:

Triumph Stag 1973 - 1975

Austin Mini 1973 - 1978

MG Midget 1500 1975 - 1980

MGB 1973 - 1978

Triumph Spitfire 1974 - 1980

Triumph GT6 1967 - 1972

Triumph TR7 & TR8 with A.C. 1977 - 1981

* for 16, 17, & 18 ACR Lucas alternators