Thanks, yes, Transferflow confirmed that. I thought that might be the case.
Well, I've got to hand it to Transferflow. They aren't making these anymore but Brad went way above and beyond to help me over the phone. It's so nice to see a company who still believes in customer service. He probably spent 30 minutes on the phone with me. He confirmed a lot of things for me, but was open about not knowing what they were doing 18 years ago.
Yes, the fuse and wiring for the rear fuel pump just piggybacks off the front, no need for a separate circuit since the switch determines that only one at a time runs. The tank is a 26 gal, and would be over $1k to replace since it would be a custom build from them at this point. Actually, I think he mentioned that if a customer wanted one they would have someone else make it, but I'm not quite sure if that's what he was getting at.
He also emailed me some PDFs on the installation which I have yet to look at, but I will update this if they reveal anything.
I was able to clean up the spot where I thought the leak originated and it started seeping again. I patched it with JB Waterweld for the moment and it stopped the leak while seeping fuel, pretty impressive. I will run or drain some fuel out of the tank and drop it when it's lighter.
After I had it cleaned up a little and with decent light I figured out that this is almost certainly a weld defect rather than a rust issue. The tank looks really good, there is no cancerous rust except on the thin strapping SMB used and underneath it where moisture stayed.