Vector1,
Your chassis originally had the JAZ 16 gallon cell installed. Did Dave change the fuel cell for another type?
I do not know which Le Mans type filler Dave used in his build.
On the standard unit that JBL uses they make the back side of the filler.
This has a separate cap under the main cap as all of the Le mans units leak. Check to see if this is what you have.
I recommend this hose.
Goodyear fuel hose
Hose reducers are quite common and and good hose supply house with have one if you need it.