With the exception of the Dana 70 3. 07 ratio, and someone can correct me if I am wrong on that please. There is a casting on the differentials, off to the lower right side of the diff cover I believe, there will be a 60,70 or 80 casting, a protruding casting not a stamp. Might be caked over with grease, dirt, mud etc. Check it out. If the ID tag was not removed by someone it would be a thin metal strip approx. 3/4" x 1 1/2", should be on one of the diff cover bolts. The gear ratio would be on there. Then there is the Bill of Material stamping on one of the axle tubes, I forget which one. That info you could look up at Dana/Spicer website, say if you suspected someone swapped in a different axle etc.