I've got a 41 chevy, 6 on 5 1/2 bolt pattern. I knew rims were going to be hard to find if you could find any at all (I can't). But all the 16" caps I can find are smoothie's?
I have never seen any. There are moon caps, smoothies (try hub cap mike), sombrero style (sorta rare), Cadillac limo caps (ultra rare) and some other small run type stuff.
Lyons made a few different 16" hubcaps that could work for you, Do a search, maybe you will see something that will work for you, but anything you find in 16" is going to be more appropriate for a forties/early fities style custom, not late fifties/early sixties.
Rims hard to find? All 1/2ton 2 and 4 wd Chevy trucks untill 1970. 4wd till much later. Will get you 15" rimd and some 16"s. Nissan trucks also had 6 lugs. Can't help you with wheel covers.