The taper of the newer ones made me think they may not fit. Good info. Mine is older with a metal frame, wrapped with some type of thin plastic like material. It was free though and in pretty good shape.
I like it better than the one I found for my 84 K10. Mine is older and actually came off a squarebody. If yours was on a non square it would be interesting to know what fits.
Welcome, you will like it here. Congrats on the truck. A rust free truck here in eastern NC is rare and gets a good price. I've seen some old squares with late model wheels but to me the offset never looks quite right.
As far as the fit for your seat I'm not sure but I will say that the cover I bought from LMC like the one in the middle of the three is a good fit in my K10. Good quality and is holding up well after three years.