First Bill, welcome to Mopar Nation, and we're always glad to have another new face, and car, in the crowd.
The problem you mention has always been here, and it all goes to numbers. Chevy and Ford made thousands of cars for every one that Chrysler made, which is why you still see so many of them driving around. They were a dime a dozen then and they still are. I think the best example of this is when you consider Chevy made more Camaros in 1969 than Chrysler made Barracudas/Cudas and Challengers from 1970-1974! Since the odds of a guy needing a part for his small block Chevy or Ford is much more likely than for a Mopar, and since there's only so much space in a store, the dealers have always stocked up on what they were most likely to sell and we've been having to special order stuff forever. But it's a lot better now than it used to be. I remember having to wait weeks for parts instead of hours or a day, so things are getting better from a logistics viewpoint.
And you can forget going to service departments. There was a run on them from the late 1980s through the 1990s, and anything that could be considered NOS was cleaned out of there by guys wanting to make a fast buck off the collector car craze. There was no gradual turnover of stock or parts knowledge because all the parts just disappeared and the guys working there today usually have no idea about older cars because they've never been in the stockroom asking "what's this old thing for?"
The up side to all of this has been that Mopar guys tend to know a lot more about their cars than Chevy or Ford guys because we have always been left to our own devices to get what we need. You ask a Chevy or Ford guy where you can get a part, and they'll know Summit, Jegs, or a local chain store. You ask Mopar guys and they know junk yards, small shops, specialty stores, chain stores, buddies, online outlets, what all the prices are, who has the best stuff, who can you trust/not trust, etc., so having that patience has made us a lot more knowledgeable than our blue oval/bowtie brethren.
We used to have to wait a couple of months for the next Mopar car show to exchange all that information, but with forums like this you can get whatever information, or leads on parts, you need very quickly.
It can be a pain sometimes, but it does have its virtues too. I can ask a Camaro owner where to get some upper control arms, and he'll say he got a set for $500 from Summit. I can ask a Mopar guy where to get upper control arms and after rubbing his chin a bit he'll say "you know, I needed a set of those myself a while back, and I remember my buddy Jim's cousin Sam had a set sitting in his garage. I think he only wanted $100 for them. Here's his number. Give him a call." Then you get to meet Sam, get your control arms, and he gives you leads on other parts you need. Overall, I like our system better.