Ray Bell the Princess R motor was my thought too !!.
Tha Valiant Healey " Healey Valiant " did have the slant six - I don't have a photo of the original Valiant motor when fitted but do have this photos of the current installation. On a slant with the lovely Webers sitting flat ..
Photo by Milan Fistonic - rebuild by the current owner - who had to take out the non-compliant V8
One of the Owners [ Grant McKenzie ] photos of the car from Mark Donaldson at the All British Day in Auckland last year I think