I live in PA (so always fighting corrosion as well) and while working my undercarriage, I noticed that mine was showing some rust. Unless I missed some trick, you need to lift the body to remove and install the filler neck. Considering this, and the fact that I wanted it in stainless, I redesigned it, reusing the top 10 or so inches of the original filler neck (it wasn't rusted and would be very difficult to fabricate a new one), and then used two stainless tubes from there to the tank. I had a shop bend 409 stainless for the main filler tub, and I bent the smaller 304 tub for the breather. This approach made it very easy to reinstall and cost less that $100 if you don't include my time to finish the fabrication and a little time welding. I do have access to a good, and reasonably priced Amish exhaust shop that bent the larger piece, so your mileage may vary. Good luck either way that you go.
In case this helps or clarifies for others, Batameez was looking for clarification / additional details about the approach above, so here are additional photos and clarification. The shop was excellent - I walked in my my filler neck cut in half, about 5 minutes later, I was in the back with and older gentlemen that started bending, which took another 5 to 10 minutes. I then paid roughly $45 (not sure exactly, and can't find receipt) and walked out - and again this is made of 409 stainless. To be clear, they bent just the larger of the two runs and there are no breaks or welds in it (they didn't have a die for the smaller line). I bent the smaller breather return with a homemade die in a press, using 16gauge wall 304, which was pretty tough to bend without kinking, but I don't think it will every need to be replaced.
The rubber filler hoses are available from Toyota, so I bought a new pair and used them to reconnect the new lines back to the tank. The old rubber lines were in very good shape and I used them to connect the lines back into the top of the original filler neck. By the way, I recommend not trying to weld to the original. it is a coated metal and will crack when welded. I tried tig and mig, with various filler wires, and the weld would crack as the metal cooled. (Maybe others have different experience or recommendation.)
The new assembly you see in the last picture slides right in without lifting the body, although I'm pretty certain the tire hanger cross-member was still out when I installed it and I'm not certain if this is critical.
I'll try to get a shot of how the lines connect to the original filler today, but here are additional photos that should clarify.
And here is the connection back to the original filler neck inlet. Of course the breather is on the far side and isn't visible, but this should give you a pretty good idea about where to cut and reconnect...