53GMC,
I just got done stripping my s10 down. Here is my 2 cents, and thats all its orth. Thadious laid out a good plan for you. I didn't keep the stock wiring at all. To me.... it was worth cutting everything out and buy a wiring kit. I went with the EZ wiring 18 circuit kit, with GM stock connectors, 175 bucks. Personal preference!!!! Keep the hood, nice flat panels for future patches. I kept the gas tank and the filler door as well. Mine is flat ('91 s10 model) so if I choose to use it, it should be a pretty easy weld into the bedside. If you are fabbing up your own cab mounts, make sure to keep all the hardware and spacers off the cab mounts and radiator mounts, you will reuse them.
You will know what they are as soon as you disassemble the cab. If your s10 has A/C, be sure to take the time and disconnect the dash controls as well as the duct work. Save the seat belts. Depending on how adventurous you are, save the door latching plates from the door frame as well as the latching pins off the doors as well as tailgate hings, all can be adapted to the '53.
First things first. Buy some PB Blaster or Nutbuster and spray down all the mounting bolts. Start with the bed, I think it was only 8 bolts. Its easier to lift the cab backwards then over the motor. The dog house is pretty easy and comes off quick. If you have enough help, leave the doors on the truck, less to mess with. If not, take them off next. It will save you about 150 lbs off the entire cab. If you have an engine hoist, build a jig and remove the cab (4 bolts) with the engine hoist.
Do Not use the jig on the 53 cab with the doors closed. It will damage the doors. I disassembled the entire s10 is about 2 hours. Be prepared, all the bolts off the s10 will be metric. I had a few old timers for assistance but I did most of it by myself. Grab a few guys and a 12 pack and you will fly thru it. Good luck and take lots and lots of pix. Like I said, this is just my 2 cents. Im sure that you will get lots of tips over the next few days.
Brian