There were two different fuel tanks and filler neck/hoses for CJ's. one for 76 and 77, and I believe the diagram posted by fuzz 401 is for the 78 and later fuel tanks. The 76-77 had a larger filler hose inlet and a different filler neck. Also the 76-77 didn't have the roll over check valve, just the liquid check valve. I have no idea what could be the difference between a liquid check valve and a roll over check valve. Both should stop the flow of a liquid and pass the vapors.
Here is a scan of the 76-77 tank for your reference. There are two diagrams here, the top is for the 76 Jeep Truck, the bottom is for the 76-77 CJ-CJ7