If at all possible, find a halfton (Chev 3100 or GMC 100). Most aftermarket repro/upgrade parts are made for the halftons. Suspension and brake parts for heavier rigs are hard to find and expensive; I spent 4 months looking for a rear drum for my tonner panel.
If you're after a Chevy and really lucky you can find a '55 first series, which will have an open driveline instead of the torque tube and full-pressure oiling instead of the splash-oil babbit pounder. A common upgrade for the early Chevs is to swap in a later 235. Smart folks just buy a GMC.
You will need to swap the rear gears if you hope to achieve freeway speeds... again, the halfton will give you a variety of ratio options where 3/4 ton and bigger do not. Both the 3- and 4-speed transmission have a final drive of 1:1 and they're tough as nails; there shouldn't be any need to swap that unless you're looking for overdrive. If you're going to push the top speed up, seriously consider a brake upgrade as well.
All the AD's were 6-volt; GMC had positive ground until '54. A well-maintained 6v system won't give you any trouble, just be sure you've got solid connections and good ground. If you want to add modern accessories, the simple way is to convert to 12v.
Once you find your truck, get a shop manual. It will take the mystery out of your project. And don't hesitate to post "dumb questions" here, odds are there's a dozen others scratching their heads over the same issue. The only stupid question is the one not asked.
Good luck, and welcome to the 'bolt.
