[DavidF1972]

This is something I will need to do as well... so I'll be watching you very closely... muhahahaha

 

[DavidF1972]

How will it be sealed?? If running a rubber gasket you would need to allow for its thickness.

 

[DavidF1972]

or silicone seal.

If just using a silicone sealant, I would use 3M 5200 it's fuel proof. I would also consider using blind holes for the threaded part. Since the tank is inside the car you don't want to take a chance with fuel wicking up the threads.
Don't mind me, I'm just thinking outloud

 

[DavidF1972]

As far as I know, there is no silicone RTV sealant that is impervious to gasoline.

From the data sheet: "3M(TM) Marine Adhesive/Sealant 5200 is not recommended for use as a teak deck seam sealer. Extended exposure to chemicals (teak cleaners, oxalic acid, gasoline, strong solvents and other harsh chemicals) may cause permanent softening of the sealant."

I've used 3m5200 for over 20 years and have never seen it effected by gasoline. I used it for sealing the crank cases of outboard motors in place of permatex #2.
It might not be "recommened" but it will certainly get the job done.

 

[DavidF1972]

Your car; your choice David.
I would not use it in direct contact with gasoline; especially in this application. If that seal fails in the GT, it will be putting gas fumes inside the car. Most cars and trucks, the tank is more isolated from the inside of the vehicle.
Besides, the MANUFACTURER advises against use where it will be subject to extended exposure to gasoline, among other things. Better off using something that IS recommended for the application.
Just thought the OP should have all the facts.

Yea ok, why don't you actually try the product before condemning it?? They the MANUFACTURER say they don't recommend it, but they don't say absolutely not!! They say it may soften I'm contact with gasoline, but not that it will. Might loose a bit of durometer, but doubt it would ever loose seal.. think about how much more abuse it takes on an outboard (2stoke) crankcase.
Hell, Ivory soap doesn't say it can plug a hole in a gas tank, but it sure will, for 30 years now...
It all comes down to liability
I would atleast recommend a test....

 

[DavidF1972]

Someone got up on the wrong side of the bed. No desire to enter into a pi$$ing match. You win if it is that important to you.

Ummm??? Did you not say MANUFACTURER?? Big bold letters???
There's no wrong side of the bed to get up on. As long as you get up