After reading this thread, and visiting
AeroTanks-we specialize in auxiliary and replacement fuel tanks.
I decided to call Jake as the webpage recommends.
I unexpectedly ended up buying a 40 gallon tank for my 2006 v10. It was a little over $1200 shipped with skid plate, freight.
I didn't think Aerotank shipped directly to a consumer and just to dealers for install. Turns out that's not true.
They are a bit behind right now, 15-18 days to ship. YMYAFMV (Your model year and fuel may very).
I should add that I have a cut down OEM tank (for sale) and would prefer in some instances to have more than 300 miles range. Additionally I think my fuel pump is going out so that is part of the project.