We do a lot of gas tank relocations on all kinds of street rods and I think my favorite for AD trucks is the early Chevy Blazer tank. The Mustang tanks fit well but the Blazer has rounded top corners that match the curve in the spare tire cross member. The filler tube on the tank is angled up and to the left so we weld in a motorcycle pop up flush fit gas cap in the back of the drivers side rear fender. All in all a tidy installation. If the pop up cap is painted body color it's nearly invisible.
21g (there is also a 13g) early Blazer tank mounted to a 49 3100 frame:
[img]https://i.postimg.cc/ZWqQ6Dhv/003.jpg[/img]No rust filler tube from tank filler neck to flush mount motorcycle fill cap:
[img]https://i.postimg.cc/75dyhyTZ/004.jpg[/img]Flush mount fill cap screws into threaded bung welded to rear fender:
[img]https://i.postimg.cc/Z98Dmk8g/008.jpg[/img]
