This certainly not unusual, and is par for the course in the service parts business today.
The "master" dbase that virtually all auto parts "systems" use comes from only a very few sources. And in the beginning, these dbases were "transposed" from manual-entry systems, to microfilm/microfiche, then to first gen "electronic" lookups. Much data was never crossed into the electronic systems in the beginning, and there is no perceived "value" in updating the lookups for obsolete/discontinued/nla items today. And all these "systems" are being purged again this year due to the economic climate in this country and the threat of the current government in eliminating "old cars" from our lifestyles. No manufacturer/distributor/retailer wants to get caught with inventory that does not roll over several cycles a year.
Some parts vendors specialize in this kind of stuff, but they have to continually "fix" their lookup dbases in a manual mode...that is a massive job...just like maintaining the online store here at ihon...it doesn't just "happen" when a mistake or inaccuracy is reported!
And you will notice that when accessing online lookups for nearly every national parts vendor, the lookup system "looks" the same" in appearance and the interface??? That is because they all use the same commercial software system!
So ya simply do your homework regarding parts information using alternative sources before making a trip to the local countermonkey. Ya "help" 'em by knowing what ya need in advance and being able to "advise" if their lookup jives with yours. And if they wanna be in denial, and act stoopid, then walk out and never go back! There are folks out there that will work for your cash and not let you leave the store without leaving some with them in return for finding the right parts for ya.
Again...we're talking 30>45 year old obsolete parts/vehicles here. It's pretty amazing in these economic times that any retailer has any part on hand for this crap. It's simply unrealistic to expect that obtaining a "normal" part over-the-counter for this stuff is still doable. We're talking ihc stuff here...not chryfordrolet that makes up the bulk of the parts bizz along with Nissan/honda/toyota.
While the 232 and 258 motors and apps for ihc are not identical, they are very similar in most respects concerning hard parts. By studying the respective ihc-produced parts lists and service manuals, and then comparing those line items with a a on-line parts lookup, you can figgr out which part is correct for whatever you are trying to do.