I see their ads, and a lot of repair shops use them. One even let me order a couple parts for a 2006 Equinox and have them delivered directly to the shop so I didn't have to pay shop markup for the parts.

The website is pretty easy to use, and they seem to have parts for nearly everything.

Good lookup on site, wide range of brands, offer new premium, OEM new, good remain brands. Has pictures!

Sometimes, you can run across New Old Stock parts for older cars/trucks, or even used parts that are in good condition and in some cases, can be overhauled.

Huge monthly classifieds all about the old car hobby. Lots of specialty cottage vendors that specialize in old cars.

Looking at one, I dont see any specific IH vendors, but there are many who specialize in various parts like carbs, alternators, starters, gaskets etc.

I agree with Rock Auto, but I have a somewhat unique old car and a lot of parts they say fit most certainly do not, so you need to take their listing with a grain of salt. RA also has no inventory of their own and drop ships everything; you can order three parts that end up coming from three different places, so they charge you shipping for all three separately which can get frustrating

The parts most frequently replaced can get out of stock. After about 25 years they're all trying to liquidate their supplies because the parts aren't moving. Then at 30 they sellout to firms that hold more permanent inventory and the price goes way up. These are general rules. Some parts will never be found again. But I would try Rockauto.com as a first source. They go way back - as to how many parts there are for 1927 - who knows. They sure won't have every part. There are others, but there's also been consolidation in parts suppliers. Those from 20 years ago got bought out. Tire suppliers for example, most of the early seller websites are defunct now, they combined with the winners.

www.ihpartsamerica.com

http://www.travelallparts.com

http://www.oldinternationaltrucks.com

http://www.thebinderboneyard.com

http://www.isasih.com

Probably others as well. Vendors that specialize in a specific make generally know exactly what fits and what doesn't in my experience. They can often be more $, but I think it is important to keep these types of shops in business instead of supporting big online places.

He found binder boneyard already, but this looks like some more good stuff.

Old Car Parts Northwest

https://ocpnw.com/

Recc'd and bookmarked for helpful replies.

Lots of ads for vintage parts dealers.

We actually have three ancient beasts running or close, so this is good for those too. Looks like Rocck Auto's the generic place and just start googling for specialties

Take a look at that alternator and see if by chance its a Delco Remy unit. If so, you might be able to rebuild it by replacing the alternator internals. There are videos on YouTube that will step you through the process. When I started out as a GM tech, one of the first procedures I learned after I finished my time working the lube rack was rebuilding alternators.

https://www.partsgeek.com/