Just look closely at Richards pictures and look at your BII. You'll easily see where to cut.
Make a panel like he did, don't try to make a small one just for the sending unit/pump. The other thing in the picture is a vent with a rubber gasket that dries out and leaks gas fumes. You get them both as one part and it's cheap. Replace the hose while you are there, use gas/fuel rated hose or it will fall apart.
Also be sure to replace your lock ring for the sending unit/pump, the old one will flatten out a little and work lose. It has like a double hump and it locks in place. Take it off and put it back and the humps flatten a little and won't stay tight. You'll get gas seeping around the ring if that happens.
BTDT on both of the above, actually a shop resused the old ring and threw away the new ring I gave them and didn't replace the vent and gasket. I had to fix both to stop the gas smell.