anybody know the door data plate codes for rear ends? door plate says 7

1979 Bobcat

? 3.40 ? I didn't think they offered that except for 1973 in a pinto? maybe I can jack it up and read the tag.

While the post isn't 8" specific, the title is enticing. So I'll throw this out for anyone interested. I believe only the 3.00, 3.40 and 3.55 were available for the 8" rearend.  Some of the ratios seem to cross over between the 6-3/4" and the 8" (3.40 seemingly one of them).

  Every time I go to Pick A Part (monthly - Sun Valley, CA) I check the 8" rears.  The majority sadly have the center sections already pulled.  There is one guy who at a minimum goes through weekly and pulls them all. Virtually all are 3.00 and a few 3.55.  When I did my turbo swap I opted for the 3.00 thinking the Pinto was lighter than the Turbo Coupe and the 13" or 14" tires would work well. Ahhh..., not so much.

 Ideally I think 3.25 would be best with shorter 13"-14" tires.  But that ratio is limited to only a few older Fords. Otherwise it is the price of aftermarket gears and setup. So my quest is now for 3.40 as a compromise.  If your running 16" tires you might get away with 3.55.  Please note these ratios are referenced to daily driving.

Tom