Coolant level, radiator overflow questions.

[domano 68]

I was checking the fluids on my "new" 72 LWB C10 and noticed the radiator fluid was low. Looks to be about 4" below the top of the radiator.

I know these old trucks do not have overflow containers, they just puke out to the ground from an overflow tube. Where is the tube located? I must be overlooking it.

How much fluid should the radiator contain when cold? All the way to the top of the filler neck, 1" below the neck ?

Is regular Prestone ok to use or should I use Dexcool? Thanks in advance!