Heater box (and everything else on this truck) is all disassembled right now,so a pic would be tough. Found that pic by Googleing "1959 Chevy heater control valve". Found it for sale at Bowtie Classics.com. Everything on this truck has been very original, right down to never having any bodywork done (or the oil changed I think).
It's running the deluxe heater.

1959 Shortbed stepside 1/2 ton project
[Linked Image from i236.photobucket.com]
[Linked Image from i236.photobucket.com]