http://www.super7thheaven.co.uk/components/sierra_rear_differential/

Have a look on the link above it may help.

Adrian

The trouble with the part numbers is that they are on little metal tags that are easily swapped or get so badly corroded that you can't read them properly.....


the link above gives you the info you'll need to work out what you've got, but if your still not sure then post a few pics and count the teeth / number of turns of the input for 1 turn of the outputs.

for a 1.8 pinto my money would be on a 7" open diff with push-in shafts and a 3.92 ratio, but I can't be sure about that as there are quite a few options and you never know if its had the diff swapped at some point....