Smart Folks Need Help? repop gas tank issue

[CJ5 Convert]

So I bought a repop gas tank because mine was ruined. I new the neck was different but the old tank was shot. I didn't keep the old tank cause it was rotten and I didn't think I needed it. Well since then I've figured out the preffered method of installing the new tanks correctly is to take the old neck off and have it soldered or welded on the new tank. I put an ad on the board for the neck off of a used tank but no takers. So this is where I need yall smart folks what options do I have. Can I safely run a fuel hose between the frame rail and bed. I think I can cut the neck of shorter. Then go get some specialty oil/fuel hose from the Hydraulics place down the street and get something that would flex in there.

But I wanted to run this by the smart people -Thanks, Jason