Checked my diff this weekend. It is a little bit difficult to tell with precision whether it's a 3.7 or not, because one of the brakes is a bit seized up and the wheel won't turn.
Counting rotations for one wheel only and the input shaft I'd say it's a 3.89

I know for sure that it came out of an A14 engined Sunny Wagon, because I pulled the car apart. Maybe it's not the original diff, maybe not all the cars had a 3.7 Who knows??