Chris, I recall this subject some time ago and understand that several 1st Gen enthusiasts have experienced the 15 gal max capacity so I have to agree. Somehow there must be some explanation for it.
That said, I drove my '68 daily for many years and never noticed that restriction. So, I recalled some old gasoline credit card receipts I still have. I found several fill-ups in 1981 & 82 of between 16.3 to 17.4 gallons.
The tank is still the factory original.
Again, I don't doubt others have found a restriction but I just cannot understand why.
