I could have sworn that there was a FAQ up on this subject somewhere on the Stovebolt page, but I can't seem to find it either.
Converting an AD from 6 to 12 volts is not all that terribly complicated. Parts that need to be replaced with their 12 volt equivalents include the battery, generator, voltage regulator, and light bulbs. Some people prefer to replace the generator and voltage regulator with an internally regulated alternator.
Parts that can remain original are the ignition system, starter, wiring, switches, and light fixtures.
Parts that will need to be protected by voltage reducers are your fuel gauge, coil, and heater motor if you have one.
First, it sounds like you're going to want to replace your entire wiring harness. There are a variety to choose from sold by vendors
who cater to old Chevy and GMC trucks. I believe that discussions on the pros and cons of different manufacturer's harnesses can be found by searching this list, or the Ole Trucks List
Next, read Patrick's null article
on 6 to 12 volt conversion, and I understand that Randy Rundle
(the moderator of this group) publishes the definitive booklet on this subject.