How do I check what gear ratio my 7 1/4 has?

Boy those ratio numbers sure sound like chivy numbers Mopars are 276, 291 323 ,355, 391, If your rear is the orig, A bodys with V8's and 7 1/4's were 291.If it was a 6 it had a 323 all the others were options .If you are lucky and you find a sure grip tag on it you scored. They made these too . I have one (323) in my barracuda . Weirdest thing,it came out of a 65 Dart with a 170 cu in slant automatic.