We have two different style cells int he 240Zs.
Mine is 12 gallon plastic foam filled RCI drag style. I made a metal holder for it. The hatch is framed in in box tubing to hole the cell in. All this has a metal cover over it in the hatch.
The fuel lines run in and out of the bottom of the cell which puts them under the car on the outside. The vent line has a roll over valve with the hose covered in conduit vented to the old filler neck area.
On the second car we used a 22 gallon circle track style bladder in a can with foam fuel cell. That way we didn't have to make a whole can/holder again.
This one required adding an additional line for the fuel return. All the lines came out of the top center of the can.
We framed in the back in box tubing to hold the cell in place than made a metal cover to go over the whole thing with an access door like mine.
We went through tech, the inspector was not initially fond of the cell in the second car. Stating the access door was not fuel tight. I think had we said more it may have gone better. I don't think he realized it was a foam filled bladder cell the roll over valves as well. That one was not my car so I did not say much during tech.
In the end Jay looked it over, we added a bit of metal tape along a the seem between the cell floor and the cover and foam on the edges of the access lid.
On my the same tech guy the access door saw a plastic RCI cell under a metal cover and was fine with it.
Both were installed more or less the same way and the first one had more layers of metal plus stainless lines and he did not like it.
So I think a receipt showing what you have plus some explaining may help.
Like Evil Genius said FIA approved cells are seriously pricey, like $800.
Troy
#35 LRE
1973 Datsun 240Z