there is an easy way to explain why you can't go to your local "Fiat-Chrysler America" parts counter and order a set of points for a 69 plymouth 340 duel point distributer - HISTORY!!
Chrysler was ALWAYS the smallest of "the Big Three" auto companies. as such, Chrysler never spent the money on "computers" or "parts sourcing" that Ford and Chevy did. further, "Chrysler" only had 2 divisions - Plymouth and Dodge. "Jeep" was its own company, then it was acquired by "American Motors" (former Studebaker) then Chrysler bought it. as everyone knows, there is no "Plymouth" any longer and "Dodge" is only "cars" - "dodge trucks" are now a separate company as is the "Jeep" division. Ford had "Ford" and "Mercury" divisions but both were essentially the same company. AND, they still exist today much as they did 50 years ago. so a "parts search" for a Ford product can still happen at a dealership. then there is "GM." everyone knows that "GM" had a number of "divisions" - Chevrolet, Pontiac, Oldsmobile, Buick, GMC. Pontiac and Oldsmobile are gone. but the other divisions still exist much like Ford over these last 50 years.
fast forward to 1998 - Daimler-Benz (the German company that makes Mercedez Benz vehicles) buys Chrysler. Chrysler was on the verge of bankruptcy at the time and Benz bought mopar at a "bargain" price and to have a domestic presence in the U.S. Daimler-Benz basically gutted Chrysler. all the internal computer and parts sourcing systems were streamlined and changed. the LAST thing Benz cared about in 1998 was Americans interested in "collecting" old mopars. and of course, a great deal of Chrysler's "written" records had to be translated into "german" and entered into "german" data bases. again, no one cared about old mopars. the last thing that can be said about the "bazaar" time "the Germans" ran "Mopar" was the cultural differences. the pre-Benz Chrysler - both Dodge and Plymouth - had a reputation as "all American" post WWII and in the 60's - a builder of "Muscle Cars!" anyone talking about this kind of stuff in a Board Room in Stuttgart were no doubt greated like they had just stepped off their flying saucer from the Planet Nibiru. the point is - the "corporate culture" of "Chrysler" NEVER even got CLOSE to being accepted or understood by the bosses in Germany - that is why Bentz had "buyer's remorse" almost IMMEDIATELY after acquiring Chrysler.
today, with Fiat owning Chrysler, at least the "hot blooded" Italians do like "fast cars." Ferarri is basically Italy's Statue of Liberty and they race their cars on the streets all over their country. so building and selling a 707 horsepower Hellcat Challenger in the U.S. - sure, that's something the spagetti and wine people can understand.
so going to a Mopar parts counter in the year 2017 and asking for parts for anything older than mid-1980's Chrysler vehicle is a little like going to a Jeep Dealer and asking the parts guy to look up a driver's side front wheel bearing for a 1946 Willys-Overland CJ-2. the part's guy is going to look at you like you have two heads. now you CAN find a front wheel bearing for a 46 Willys CJ-2 - but you're NOT going to get that part from "part's computer" at a current Jeep dealership.