Found him and the thread... https://forum.ih8mud.com/100-series-cruisers/95328-100_series-aux-tank-install.html
His name is Scott, may want to PM him.
And here is the website for the west coast guys... Specter Off-Road, Inc. Land Cruiser Parts and Accessories
It looks like Scott (mobi-arc) ended up getting the wrong part from Specter Off-Road. He got a 80-series dual filler neck which turned out to be a PITA to install in the 100.
Someone else mentioned in the thread that they have had issues with Specter like that as well.
I did spend quite a bit of time trying to find a 100 series dual filler neck on their website, but no luck. All they have are 80-series. With that, and the unfortunate cases of shipping wrong parts, it looks like Dave at Japan4x4 is the way to go.
I will let you know if I get some photos of the parts. I am pretty sure I am going to go this route...FR tank with OEM dual filler neck modifed to accept hose from fuel pump on the FR tank, which will be controlled by the OEM sub-tank switch up front.
I don't know how many guys are running either OEM sub-tanks or long range tanks, but it would seem like it should be a popular upgrade with how many people are buying rear bumpers and throwing their spare tires up there.
I wonder if there would be a market in bringing five to ten of these dual filler necks?