Borg Warner rear end, as used in 1976-78 120Y sedans. They are the same width as the 1200 diff & somebody in the past has replaced your original H145 diff. I bought a 1200 coupe for parts in 1985, mainly for the A12 5 speed & it had one of these in it. Drove the car home then wrecked it out, cause the repair list to get it registered was 2 foolscap pages long. it was dark green with a vinyl roof. Long time past.