While browsing a couple of parts sites in the US I came upon a description for a flip-top cap and the inner rubber seal we spoke of earlier in this post. Apparently you can buy this to suit your flip-top cap as described below. The supplier is Laysons Restorations
www.laysons.com This might help those of you in need of a sealer or cap to suit the inside filler neck.
Flip Top Caps
One of the most eye-catching styling elements Chrysler used on 1967-71 A and B-Body muscle cars was the flip-top fuel cap. These caps gave the cars a bit of "stock car" styling for the street. Each cap features brilliant chrome plating with the correctly detailed appearance, spring-tensioned openings, and the high quality rubber seals that seal the caps to the filler tubes. These caps do not include the mounting hardware. We also have the trim rings.
Part # Description Price Qty.
FS-671 Challenger flip cap seal - with attaching hardware
70-74 Challenger $14.00
IN-FR63 Fuel Cap
70-71 Challenger $139.00
As you can see from the above prices - the cap seal is relatively cheap in comparison to the cap itself...