We used a 20 gal. Mustang tank in the 64 Falcon project.  We welded a tube stub up about midway on the custom fuel filler neck and toward the top (or front) of the neck so sloshing fuel would not get into the vent tube...although the Falcon had the vent on top of the tank an it apparently wasn't a big problem.  I did the same thing on my Mustang to add a vent to capture the excess vapors caused by the recirculating EFI fuel system.
I don't have a pic of the fuel filler but here's a couple of pix of a really nice 64 Falcon.  They drove it to Wichita, KS on July 15 for the national Falcon gathering...they had a blast and the car performed flawlessly once they got the AC charge tuned up.  And it did 24 mpg.
Also, I presume your PM is asking for my Gas Gauge Gage info.  I'll get it on the way to you.

BB






 

Last edited by Bullet Bob (8/03/2018 6:52 AM)

The Falcon will vent the tank in or out, I think and the gas cap is sealed.  The Mustang, or at least the 66, is vented through the cap and will only allow air in but does not allow vapor or pressure out.  I discovered this when I went to EFI and drove to Kalispell, MT and back and the new fuel tank swelled up like a beach ball.  That's when I decided to go to a separate vent line into a charcoal canister and re-enable Canister Purge in the computer.
When we first put the Falcon on the road the owner drove it back and forth to work for a couple of weeks and complained of heavy fuel smell in the trunk.  Her husband checked every thing and discovered he had two or three pinholes in his weld on the custom filler neck he had made.  Fixed that and no more stink with EFI and the stock Falcon vent tube exiting at the right rear of the car.

BB-