Like others have posted, I can't say that I was influenced by either Keith or OC, as they were a touch before my time.
I will say I have spent the weekend reading "Hell, I was there." and I gave up on an earlier attempt to read "Sixguns".
I don't know that I have ever had an opportunity to read OC, per se.
Aagaard and Askins were two of my favorite writers when I was growing up.