If I recall correctly, my caps just have the nyloc nut on the bottom. Put on the new O-rings and tighten them a little at a time until the cap wont turn in the fuel neck when the locking tab is down. They should remove freely when the tab is up. If you tighten too much, you will knw, because it will require some wiggling to remove the cap with the locking tab up.
I think thatís the way the cap in the right wing works. The one in the left wing is different and looks like the picture posted earlier. Iíll go up and put the new o ring on but I suspect I will buy a new cap just so they match.