Button, great about the pump pulley. I too drive a 7.3L IDI truck (1990) I have found quite a few things are hard to source when making some repairs. Fortunately, if maintained well, repairs are rare.
The poster falls under the category of advertising and entertainment, not historical archive.
The poster is something fun to look at while waiting. With current computer graphics and photo shop capabilities a good graphic artist can pretty much make up anything they want...You know this already.
The vast majority of people looking at the poster would not know the difference between historically correct and custom made so it makes little difference anyway.
When you see a poster like this being used as a guide or reference THEN you have a legit issue worth bringing up.