Here's my book on the subject.
While I've not 'restored' my 63 Dart wagon, I have rebuilt the engine and repaired/replaced many parts. The next two projects for the car are rebuilding the front end, and installing the optional factory-issued, dealer-installed "Cool Aire" air conditioning.
Most of the integral engine and chassis parts easy to find new at places like RockAuto.com, Napapartsonline.com (sourced online but picked up locally), Oreillyauto.com, etc. ***manufacturing quality will vary depending on brand and country of origin*** NOS parts can often be superior to newly-reproduced parts but are usually twice or thrice the price and it's not always/often necessary to go this route for anyone other than the most persnickety individual. Radiators are an exception to the easy availability of engine parts: there are NO reproduction rads I found anywhere that were close to acceptable if you want a stock appearance of your engine compartment. I had a new one custom-made through Randy Pettey in Michigan and I'm quite happy with the result. It wasn't cheap. You could try finding a good used rad from a donor car, but it's hard to tell if they're good until they heat up and don't leak (and last).
Most everything else is going to be sourced through eBay, this website, SlantSix.org, and personal one-on-one transactions through swap meets, and various parts vendors.
You'll likely have an extended search finding wagon-specific body parts, exterior trim 'jewelry' and interior plastic parts (try sourcing a good interior C-pillar plastic trim cover, or the same D-pillar cover). Also, depending on whether your wagon is a 170 or 270, you'll have more to find if it's missing.
For instance, tailgate hardware doesn't exist for the most part. I think you're best bet is to find a parts car with a good tailgate (which can also be tough to locate since these were rust-prone from the inside out if the tailgate window rubber seal is cracked), and keep the tailgate and rob parts from it as you need them (or find a tailgate better than the one you have and replace it completely). Station wagon rubber is another headache: I don't know of anyone right now who's reproduced replacement cargo window rubber gaskets. Unless you're doing body work on rusty/corroded window sills, I'd leave the cargo windows in, even for painting.
The taillight assemblies to a 63 Dart wagon are unique from the 63 Dart sedan and one-year only. The lenses had chrome trim rings, most of which fell off a long time ago to the point of being nearly forgotten today until you look at the parts list book for a factory illustration. The lettering spelling "DODGE" on the tailgate for a 63 is also unique and one-year only. The optional reverse lights are wagon-specific because of the curvature of the body panel where they're installed, but the lights are the same between 63 and 64.
Good floor panels that replicate the originals can be had but are pricey - trying to remember the name of the vendor. Reproduced wagon floors (cargo/spare tire compartment) aft of rear passenger seat don't exist and you'd be looking at sourcing a donor floor from a parts vehicle if yours is bad. Most any other floor panels you find will have to be rolled & cut to fit your floor by your body shop.
You're going to have to look hard for the optional accessories if you want to deck your wagon out with the factory goodies (the list wasn't that long). I searched a long time for the A/C equipment and finally got lucky. Tailgate electric rear windows are not common so if you can find one with the setup (or if your wagon has it already) count yourself lucky and restore what you have. You'll be sifting through donor cars to find parts for these setups, or you'll be paying through the nose from individual parts vendors since they usually research and know what they have before asking $400 for a tailgate switch.
Here is a thread that's been useful to me a few times:
http://moparforums.com/forums/f13/some-nos-gently-used-part-suppliers-9000/
Feel free to PM me if you want to talk more specifics and good luck with your wagon: post some pictures of what you're starting with. I've owned mine over 17 years and it's a fantastic old car. Reliable, with love-it-or-hate-it styling. Not everyone likes them but their devotees constantly sing their praises as their utility is well-known. I actually hauled a cast-iron porcelain bathtub in mine and the wagon faithfully delivered. Probably wouldn't do it again though.
