64 Barracuda rear end

I'M not savy on rear ends on a 65 cuda. So how does one tell if its a 7 1/4 or 8 3/4? Gear ratio on a stock 65 cuda 273 2 barrell automatic floor shift?

7 1/4 has a cover that bolts on from the rear and 8 3/4 does not have a rear cover.