When I installed the gas tank in the car in the picture above, I used contact cement to glue old fashioned friction tape to the top flange of the cowl panel. I punched holes for the 5 bolts/clamps that hold the gas tank to the cowl. I figured this would minimize or eleimate any squeaks between the metal parts. In fact, I did this in many places as I reassembled the car, which I had totally dismantled to repair the numerous rust holes. From what I have seen the anti-squeak that vendors sell it too thick and costs a lot more than friction tape. Friction tape will only stick to itself, so that is why I glued with contact cement. The welting serves to eliminate any squeaking where it is applied.
Rusty Nelson