The first task after receiving the car was to take it apart which I considered the first step. Seeing all the projects I started working on the tanks install. I have been looking at using a AN 16 size line between tanks and it appears there is room to run the line outside the cockpit in front of the engine, still working on it. That's just one of the challenges of a Mk IV with only one filler. Original cars had this line running under the seats which was the first idea but since there is a way around the cockpit it's the new plan.
The holes are cut and tanks slide in and out fine. I found the tanks are 44 1/2" long while the side pockets where the tanks fit is 48 1/2" long which gives us 2" front and back. Someone did the math because the filler hole lines up where the tank sets when centered in the side pocket. Doing the volume calculation the tanks are about 10 to 11 gallons each. Tanks will have fuel cell foam as others have done.
Been searching for fuel lines and fittings. The tank fuel supply opening are tapped 7/16"-20, and best I can see require a o-ring fitting like used on carburetor supplies, see attached photo. Vent is tapped 3/8" which is easy to plumb. The fuel sending unit needs to be cut to length and I tapped the screw holes for 10 x 24 x 1 1/4" long screws.
The supplied filler neck will require a lot of modifications to make it fit in the space available, see photo. But like all things with the build everything is custom by the time it is done.