Well it depends on what he means by an RV wheel. There were 8 lug 19.5's (we always call them "Frito" 19.5's since they were used on the heavy 1 ton step vans that were most often seen as Fritos trucks) and they had a 4.56" center bore. 4 hand holes. Look like this:
Or you had the real deal RV chassis that was similar to the 3500HD, those are 10 lug 19.5's with a 5.25" center bore. 5 hand holes. Best pic I could find, sorry.
Both are made by Accuride. The 8 lug ones are probably a little harder to find than the 10. I posted the part numbers to both a while back, can dig them up if you need them.
What's confusing to me is if your guy is looking for some old 19.5's all he is going to find is steel...maybe I misunderstood what's going on and am pokin my nose in for nothin.
Richard