The 6 volt coil and condenser are fine. Buy an ignition resistor for a 1957 Chevy PU truck and install it under the dash in the line feeding the coil. If you want, install a 1957 Chevy brake light switch on the passengers side so that it follows the starter linkage (part over bellhousing) as you step on it. Connect this switch across the ignition resistor. It will start better when cold. This is what they use to do before electronic ignition, i.e. short out the ignition resistor when starting.

While you are at it, I install the same switch on the drivers side for the stop lights. Again it follows the pedal and the minute you press on the pedal, the stop lights come on. A much better setup.

Disconnect the vehicle power lead coming down the cowl that powers the truck from the starter and run it back to the battery directly. To be a little gentler on the starter, you can install a new battery cable, a thin, modern one. This will act like a resistor and take some heat from the starter,

Install a mid 70’s GM alternator. 35 amps is plenty. If you go for the bigger 63 amp one, you may have problems with belt squeal. You will need to make a bracket to push the alternator out from the engine. Use a 6″ pieces of 3/8″ rod with a few nuts on it to hold the alternator and position it front to back.

JC Whitney sells a voltage REGULATOR (not resistor) that gives you a regulated 6 v for the gas gauge. JC Whitney part number: WA710376Y $17.99

You can take the WW2 tail lights units apart and replace the bulbs with 12v ones or try and find the original WW2 12v ones which are somewhat scarce.

There are NOS resistors (original WW2) for use with the BO headlight when running 12v.

Electric WW2 trailer brakes are handled by connecting the brakes in series instead of parallel. Connect one lead from one wheel to ground. Connect the other lead from that wheel to one lead from the other wheel. Take the other lead from this second wheel and connect that lead to your electric brake trailer connector.

If you have a tandem axle trailer like a Searchlight Trailer or Generator Trailer, do the above procedure for each axle and bring the lead from each axle to the trailer connector.