I've got the Con-Ferr tank holder just like that. The difference is how I mounted tothe spare tire rack. In the center of the spare wheel while it's mounted on your rig ,you will notice a smaller diameter hole that is on/in the tire mount itself. If I remember correctly it's around 4". This is where I used a steel galvanised 4" pipe reducer behind the hole to secure a short length on the outside called a coupler ( 4" Galv. steel ). This always stays on the truck. Now for the con-ferr part , I constructed a 1/4" plate roughly 4" x 6" with 4 holes to bolt to the existing holes on the con - ferr. To this flat plate I welded a 2" long section of threaded steel that fits the coupler that is always mounted to the truck. When I want the extra fuel can on I just spin the can/mount on . It takes about 15 full spins so there are plenty of threads engaging. As a bonus when I fill other containers I just tilt/twist the whole can over to one side so I don't have to lift and most likely spill. I siphon mostly. Sorry about long explanation but I have no camera. When I did final tightening of reducer/coupler on truck I indexed it in right spot so that when spinning the fuel can on it tightens/bottoms out at a straight up position. Also when I installed th coupler/reducer I used a HUGE pipe wrench. No lock-tite or anything and its been there for years (probably rusted on). Also the protruding coupler aids in lifting your spare tire on. The wheel goes up onthe coupler and holds it there and then you spin it to match the wholes to the three lugs. Good luck.