Help - Who Put Paint Thinner In My Gas Tank!!

[hdflstf]

Got the old spare aux tank out and it looks like I need some parts to get it up to operational again.
First picture - need a new gasket for the sender unit.
2nd - need some info on the 3 standoffs. Looks like they used some sealer at the base and on the inside. Anyone have the scoop on them?
3rd - a couple of reasons why no gas was coming out of the tank. Misrouted hose completely smashed between tank and bed rail and cracked through at tank.
4th - Mounting hardware is very rusty. The bolts are necked down from rust so I'd like to find some replacements. The special nuts are not great but I can cut the welded on nuts (had to weld them on to get the nuts to turn..) if I need to.
5th - Filler neck doesn't appear to be entirely correct. The screw holes don't line up with the holes and clips that are part of the truck so they made another set of holes. Any thoughts on this one?

TIA