Did a few fuel cells as well but these were made to Iron Butt Association requirements and were specific to each bike - as they were only allowed to carry around 11.5 gallons at the time. Had internal baffles welded in, tip over valves, electrical grounding block, etc. Powdercaoted this one to match a bike - ugly as shit. Usually powdered them black.
I used Summit Racing car fuel cells and cut them open to add baffles and reduce them in size. It was cheaper to buy from them than to buy aluminum sheet stock and completely make my own. Plus, I got the fittings with them , etc.