It has a tag on the lower left side of the diff cover. That should tell the ratio. For the record, I have NEVER seen any 7 1/4" axle in ANY ratio other than a 2.76. I know they supposedly had other ratios but I have seen maybe 25-30 in my time and every one was a 2.76.
There were many ratios for the 7 1/4. I have a 3.23 in my 64 Valiant, a 3.91 SG and 2.9x open drum to drum in stock, Also 3.91 and 5.13 gear sets on the shelf.