55.2-59 Help please.....door hinge, coolant reservoir, horn wiring

[Missyblue]

I'm hoping to get this girl on the road and hitting a few road blocks so need the experts!!!! We got gauges all working except speedo so far so pretty huge victory there! And she starts and runs for 90 seconds and dies so working on relays haha but my next jobs I'm a little stuck.......

1. Hinge.....top bolt is missing the nut on the backside...looks like they cut part of the hinge area out to accommodate.....am I good to just try and get a nut back there with a wrench somehow......debated like a jb weld but worried I'll get it in the threads.........although my dad has a tap.kit if I do 🤔 I also have several in my bumper bullets that will be this same problem...

2. Coolant reservoir......any reason i shouldn't put it here? Havent seen the truck fully together so trying to understand what might attach onto the filler panel....theres lots of holes in it haha.....I have a 1957 if that makes a difference

3. I have a 1979 gm van column and a aftermarket wiring harness......is this the wire for the horn? I have a 3 prong horn plug off the wiring kit but dont know if these tiny wires are meant to be for that or cruise control haha. They have a plug that looks like the plug when I google a new horn harness for the year......basically any help on horn wiring and also horn placement would be appreciated.......I'm almost done with rear wiring so researching front.

4. Also going to drill holes for seatbelts......how do you not accidentally drill through to the sky haha.....someone said maybe I can tape the drill bit for the shallow depth between metal layers?

Thanks!