2. Dimmer switch is located at the steering column. Easy to access.
Try with a voltage meter, a green wire should turn hot when hi beam
switched. A relay is a good idea to add in the circuit, considering the
power consuption of 4 beams.
Wipers are not working at all? Try and connect ground to the wiper
motor unit connector at the firewall. The connector with more wires, one
is hot and the speed control is by grouding the other pins. If the truck
has intermittent, the black control box is underneath the steering column.
4. no worry about cold white smoke, as long as oil and coolant
stay where they belong and no bubling in the coolant reservoir.
6. unless you are not carrying heavy load or nascar racing with
the truck, the rear brakes might be enough
7. you can easily wire the radio from the fusebox too
8. try to increase idle speed. You have to turn the accelerator
lever at the pump to reach the idle stop screw. When old these
engines like to idle a bit higher, otherwise they'd shake.
Also worn engine rubber mounts allow the engine travel side to side.
And this is important: change the harmonic balancer asap,
if you don't know the age of it. A broken crank could result.
A new balancer might smoothen a bit the idle too.
10. keep the air filter clean. If the engine has +100k,
you might want to increase the fuel injection advance by turning
the pump, to compensate stretched timing chain. You'll feel
the difference in power. But be moderate with the extra advance.
Happy truckin