Thanks!
I've been a bit lazy on the car but a new part arrived, a fuel tank that matches the roof :-)
Thanks to Hector and the guys at Rick's tanks. This is their Vaporworx tank which runs corner pickups and a dual pump module from a 2012 Cadillac CTS-V. It's brushed stainless and has a 26.5 gallon capacity. Stock tank is 20 gallons.
Just need to get some brackets. (It will be mounted to the frame).