LMC Truck Parts is uninterested....

After years of investigating the GM interchangeability of parts I've needed for my 69 van and buying many of them from LMC truck/ Long Motors.....
I wrote them a letter yesterday, proposing to help them identify c10 parts that also fit g-vans so that they might be the first to publish a catalog of parts for our vans...
I received a robotic boilerplate reply from a "communication specialist" named Dakota C. basically saying they could not "advise" on the fitment of parts for vehicles that those parts aren't listed for.....
I'm guessing that Dakota C. is far removed from management, but wonder why they would advise their "communication specialists" to not forward to management suggestions that would make them money.....
Who is in charge of LMC (?) and are they incompetent(?) or are they just so busy selling c10 parts that vans don't matter?
If LMC doesn't want the business, maybe one of their competitors would be willing to publish a catalog (?)

You can lead a horse to water…but you can’t make him drink…even if it would be great for him!!!

They wouldn't even need to print a separate catalog....They could simply label the catalog "60-66 Trucks and vans" and "67-72 Trucks and vans" and ID application/fitment of each item in catalog where they already have it displayed....
A few trusted customers could be commissioned without a lot of expense to help them sort through what fits the vans and what doesn't... Maybe even as little as free shipping for returns for R&D volunteers would do it.....
I just can't believe that after building a business producing repop parts, that the business owner would not do everything possible to make those parts available to everybody that can use them....

I know this is an old topic but would you consider making a list here for new van owners? That would be incredibly helpful I just made a deal on a 69 and am sure parts will be hard to find.