I hear the Frontline LE60 before I see it. A small enclosed trailer quakes to its V-8 soundtrack and it gradually backs down the ramps and reveals itself to an otherwise unremarkable day in the U.K.

This is where things really started to heat up in British Leyland’s battle of the brands, because the Triumph Stag is the reason why the V8-engined MGB came only in GT form. Despite Ken Costello’s ...