The new gauge is not only being offered on the new kits but is also available as a retrofit on existing tanks for around $70 at the time of this posting. Its part number is "12 fuel tank mod". This is a cool addition as now one can tell how full the fuel tank is while filling it up.
Kind of wish I hadn't built my fuel tank. But I think it is worth the extra work. I will make sure to document my experience with the installation.