I always figured parts would be a bit of an issue here in Oz although I've run big American cars before without problems with parts, not good to hear that the parts supply seems to be drying up.
For US forum guys - this rant is for the "other Australian guy" and may not suit/be applicableyou may not care.

. Feel free to scroll past now.......................
It used to be that the QA for parts was what people would tool up and make. 20 years or so ago, most wouldn't bother to tool up and make rubbish. Then they did. So the QA used to be what reputable dealers would sell. That now gone as well (mostly).
You have to have a feel for the parts yourself. Find out what genuine are worth first = have a benchmark. I am in Australia (WA) like you, and the cost of parts are one extreme to the other. Our headlights are THREE GRAND EACH here - which is ludicrous. Overseas market lights don't work (RHD/self level) and wreckers know what they are worth. The FIRST thing I did with mine was defeat the self leveling; as it just doesn't work/constantly blinds others. That's another story.

And yet a door handle for my car is SO CHEAP compared to other cars. So KNOW what the stealership want for them for a start.
It appears that the levels of price/quality (here at least) are "original" (should be good, but expensive) and at the other end, parts that are almost free. There is ONE guy here who fixes these cars that I know of, (has a good rep, no names, no court martials............) and I got my bits from him, as the ultra cheap ebay prices seemed dodgy. It appears you have to get him on a certain day, as when I bought my suspension struts (those "tension struts " I mentioned) he was the most helpful guy ever. Next time I called him for something else, he bordered on abusive, because I "dared to ask a question/provided some info/dared to "know something about my car." Maybe he was under the pump........and fair enough. maybe he gets lots of idiots with stupid questions.....................
Going back to my "used to/rep dealers". I have 4 bikes and 4 cars, oldest 1963, newest 2016, but most older (63,69,76,76,2006,2007,2016); and do everything myself.
I ordered a master cylinder for my Jag. Now, this is brakes. From a reputable seller. The seals were useless. They didn't seal when on the bench, BEFORE any pressure. Housing/bore was good (within tolerance) so I bought a genuine kit and rebuilt it = good as gold. But point is - a leading/reputable aftermarket seller selling BRAKE parts with seals that just couldn't work. I could tell they were rubbish by looking at them; they couldn't, and supplied brake parts that were useless/dangerous.
I rebuilt the 63 BSA. Some parts I bought 4 times, as 3 just weren't good enough. HALF the "new" parts - in a box now, as my old ones better/reconned them after seeing what crap "new" were.
People who work in these places now (most, not all) are "store people", not hands on. Bike forums report that "all a certain sprocket made wrong/have to machine". I call them (supplier in UK) tell them to "go to this parts bin" = parts in there correct. Tell them to swap those in that bin with this bin = fixed. They were in the wrong bin = they just didn't know. So I have to call/get them to measure/send a photo. What the???? They were good about it (many just get abusive). Suspension bushes - 29 places selling a bush that DOES NOT FIT until machined - because all made by same supplier. All made wrong.
Now, many will say "off track/not Chrysler"; but almost everywhere is the same now. The people selling them mostly "look in a bin at a part number" and have little idea what's what; or whether any good/will work.
The most common reply I get is "none of our other customers have had any.......we sell heaps of....." Maybe because the average person also has as little clue of what a quality part is.
I rebuilt the rear brake cyls on my 76 Stag. Girling kit is TWICE what a whole new slave cyl is. Girling kit WORKS. The whole new slave cyl is EIGHT DOLLARS. Everyone says I am the idiot, "why not just buy whole........" ; but - I don't trust that. It would have those seals in it that just don't work. You can see/feel that they are rubbish - But LEADING parts people sell them. 'Again - None of our other customers have said........." For rear hubs, I have made my own parts, as the new ones JUST DON'T WORK.
Like I said = not Chrysler. But my experience is that the entire industry is getting like that, (here, in Australia/ordering parts that come from OS. The USA MAY be different, but I comment /provide background because we are in same country) because WE (fix ourselves) are a minority that they industry cannot wait to get rid off, and we are "dying off/dwindling" very quickly. MOST "take to a place" and they replace entire assy's/tell you to buy a new car.
So, the point is, you have to learn to judge parts based on what you are willing to trust/accept. This forum is brilliant at informing about what/where/is available; but during my two years total rebuild with the BSA (and now a 74 Trident bike) parts from the USA are often prohibitively expensive. Post costs are VERY variable (from state to state?) but they started to go up when covid started, and are now very high.
The US mail is brilliant, and their tracking is great; but once the post gets to be 2/3 times the cost of the item.............. getting back to dealer prices. I understand clunky is heavy and it costs what it costs, but before covid I used to buy half my OS parts from the US, now it just isn't viable, as the post prices haven't come back to pre covid levels, and may never do so, so anyone here has to weigh options.
Apologies to US forum goers for all the above. Scroll by if not relevant. But I thought it may be of interest to the other Aussie guy. And if he is aware - better to give suck eggs than not.
Cheers. Happy New Year. 😎