Replace door jamb??

[airbrushguy]

I have a buddy who owns a 1970 K20 and has had it at least 30 years. He showed me a problem he was having with the passenger door not shutting completely. When I tried to see it was difficult to spread the door open enough to see clearly but it looks like the cab's door frame had rotted where the bottom hinge mounts and the hinge essentially was no longer connected.
This is probably serious enough for most to say scrap it or get another cab but, this is his baby, even though he still uses it as a partial worktruck.
Does anyone sell a replacement panel for this area? I do not know of a junkyard in my area that has one of these trucks that I could cut it out of yet I don't want to not be able to fix this for him.
Any ideas would certainly be welcome.
Thanks