[papajam]

Yes, the US bound 2l Alfas from 72-80 (or was it 81) were fitted with a 4.56 LSD as standard equipment. In 80 or 81 the ratio was changed to 4.10.
The LSD differential housings have a ribbed casting in the shape of a triangle that the non-LSD diffs don't have. So you can tell to difference without opening up the rear. I'll see if I can find a pic......

Oh, and welcome to the BB!