Finding parts for a classic car can be difficult if you're trying to restore it. Parts may or not be available from the original manufacturer depending on the popularity and vintage of the car.
The manufacturer will usually charge a premium price if they are available, as there is less demand for these parts than there would be for parts from newer models. You will need to find parts elsewhere if you can't get them from the original manufacturer or dealer.
If you are a truck owner, trying to find an affordable part replacement, you can look for collection truck junkyards nearby. These junkyards contain parts from used vehicles that are still working in good condition.
Other than that, here are a few options where you can look for auto parts:
Get together with other Enthusiasts
You may be able to find contact information for parts suppliers if you join a club or website that focuses on classic cars. Many enthusiasts may have parts that they don't need anymore or are willing to trade their cars. It is possible to find parts, but there is no guarantee.
Shopping online is another option. Many classic parts can be found on eBay and other online classifieds sites. Online shopping opens up the world, so if your search is for something very specific, there are more chances of you finding it.
Remember that you won't be able to inspect the parts before purchasing. You should ensure that the listing on the internet has detailed photos. You still have the chance of getting a part with rust damage, even if you have photos.
The Junk Yard is your best bet
As said above, you can also visit a junkyard. Junkyards take in vehicles of any year, make, or model. They salvage all parts from the cars they receive. You have a high chance of finding the right part for your classic car because most of the cars that they accept are older.