Can anyone tell me wot is the best suited diff for 2.0 pinto with and 1.8 type 9 gearbox is?

The diff in my 2.0i donor car was a 3.92, I wanted a slightly longer gearing due to the slightly reduced weight of the car (!). I found an axle from a 1.6 capri which was 3.75, if I use 185 60 13 tyres the gearing will be almost identical to the donor so I can use the clocks for the SVA and then use 185 70 13 once I have stripped the 60's of any useful tread!