All Sierra and Granada 4x4 rear diffs have LSD, regardless of engine (except Scorpio from 1994 onwards as that had an open diff but electronic traction control).

I have a 2.0 DOHC 4x4 with an LSD as standard using a 3.92 ratio (even says it in the Ford literature, repair manual, parts catalogue, spec list as detailed on the production line).

I also have a 2.9 4x4 rear axle with LSD using a 3.62 ratio sitting in the garage for my other halfs 2000e.

Also, I'd would recommend listening to Mick. Between him and Dojj, they have probably taken apart more Sierra and Granada cars and diffs than most Cossie owners have broken.