Sealing 1969 GTX Quarter Extensions

[threewood]

I looks and didn't come up with any results. Have the extensions primed and want to spray them on the vehicle. I have the 2 plastic gaskets that attach with 3 plastic push tabs but it doesn't seem like it would work.

Is there another, softer gasket that seals better?
Has anyone used seam sealer in the seam?
Pictures would be helpful, thanks!

 

[Pistol Pete]

Seam sealer would be the best bet. Just make some tooling to dress the gap evenly and you're on your way. Nice thing about that method is if you don't care for it (or screw it up) you can take the extension off, remove the seam sealer and start over.