Help Installing fuel filler tube grommet and vent tube on a 69 Cuda fastback

Just to clarify, the tank seal is a donut that has to be fitted into the tank opening before you insert the filler tube. The filler tube needs to be more or less in place in the car, and you have to wiggle the tank up on it while you wiggle the filler into it — if either one is bolted in place you don't have enough "wiggle" (at least, that's my experience). And obviously, the filler tube goes through the flat seal in the trunk floor (which is different than the one in the coupe). But anyway, you have to drop the tank out completely to start. It's insane that the previous owner didn't have the tank grommet installed correctly.