So I unbolted both tank straps. The tank won't budge. The filler tube has a rubber extension that is bolted to the INSIDE of the frame rail.
So I hacked a hole in the floor. I didn't like that carpet anyway.
Despite my totally random selection of section to cut, I hit a bulls eye. I can see all of the lines and I can get at the hose clamp for the filler tube. The lines are clearly rotted. Problem is the feed lines attach to the tank under the bathroom. I either have to figure out how to drop the tank or hack another hole in the bathroom floor. The bathroom is carpet, too, and I wouldn't mind getting rid of it.
I wanted to replace the carpet with tile or fake wood anyway.