The trans should have a tag on the side. It should have all the info you need on it to figure out what it is.
Brakes I can't help with as I have air.
You'll have to look at harnesses from another 1965 truck, a C30 for instance. I could not find anyone that could guarantee the whole harness would fit my 1969 C60. I looked up all the wiring from a C10-30 and what I found was most of the wiring was the same just a different color or route, not all of the harness worked until I replaced everything with the C30 harness. I delt with this place
http://www.wiringharness.com/ and took the gamble. If you call them they'll get you taken care of and tell you what harnesses you'll need. All and all it cost me just over $1k for wiring. They custom make each harness and take forever to do it. I was emailed every excuse in the book about lead times.
Be sure to also replace your 2 speed wiring on your shifter, if it hasn't gone bad yet it will soon. That can be bought elsewhere for around $50 if I remember correctly.
I added a used 50 gallon fuel tank to my truck and after draining and playing hell trying to get it clean I ended up draining it and power washed it then used my shop vac to get as much water as I could out. Then power washed it again and again. Multiple fuel filters and a final cleaning it hasn't given me any other issues. I have a 1/2" drain at the bottom of it to allow crud to fall out.
Ohm your sending units, they may work just fine. I wouldn't be surprised if your float fell off or has a pin hole in it after all these years.
Try looking here for tire information. I'm sure what you're looking for is there somewhere.
https://www.stovebolt.com/ubbthreads...tml#Post867617