Not sure you got a complete answer to your question. Welcome to the group and your project.
As to parts, the sources listed are good, but don't forget the auction sites or other sales sites like Ebay, Craigslist, etc. There are many out there so do some Google Searches to find them. I use all the sources listed, and also participate in forums for other clubs, like Ford or Pontiac forums. They will often mention other parts places that might carry Chevy parts too since some were interchangeable.
If you visit auction sites, don't get into Auction Fever and overpay. You have to bide your time, check things out, and get into the "game" so to speak. Too many folks overpay by buying the first item they see that they need, and then go down 10 or 12 auction items and find the same item for less than half the price. So be patient, know the real values, bide your time, and remember that if you don't buy the overpriced part you see right away, you will see another one down the road if you are patient (which is hard when you are restoring a vehicle and want to get done). Lately I've been seeing some really overpriced, in my opinion, 28 parts. I have quite an inventory and am always looking for future parts to acquire at a decent price. Same for my wife's 61 Corvette.
Good luck on your project. Sounds great. Wish I had a truck but I'm satisfied with my 2 28 Nationals. You can see them at
www.theforgottenchevy.com