The car is a 1963 Plymouth Savoy. It has a PCV valve that threads into a 90 degree brass fitting that attaches to a metal cup. Is this original to the car? Where can I get a replacement?

Yes, that's the type that was factory-installed through 1963.
If you want to stick with this type of valve, the original is an AC CV-624C. They are all over eBay, inexpensively; see here. You'll see that some of them are larger and some are smaller. The larger type can be disassembled for periodic cleaning; there's a snap ring at the bottom which you take off, then take the parts out and clean them and the body and reassemble. The small type cannot be disassembled. The black valve you're showing is a Stanadyne-made item, basically the '64-'69 valve without the pressed-in, curved metal elbow which took the place of the separate brass fitting (that kind of valve looks like this). The '64-up valves are designed such that they do a better job keeping themselves clean than the original-type '61-'63 valve; also the '64-up valves make less noise (rattle) — and can be cleaned just fine with spray carburetor cleaner.

Whichever type of valve you wind up using, you have to make sure to use the right one. There were two identical-looking ones of every type, one with less flow for the 170 engine, and one with more flow for 225s and all V8s.

That cap the valve fits into, looks like a spray-can cap, is meant to be painted black.

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