You'll have a really hard time finding 16" wheels with a 5 on
4.5" pattern. Last ones I can think of were the 16 x 5 (sometimes 16 x
5.5" or 6") Dodge/Fargo pickup wheels up until the early '70s. "Split
rims," they were called, but weren't really. Had removable rings.
Split rims had the split down the actual center of the wheel. A real
pain. WWII sort of stuff.
      Terminology: "Wheels" are what you are looking for. A wheel has
a center plate of some sort. A rim has no center plate, and is usually
mounted on a spoked hub using clamps like you might see on really old
cars and a lot of modern logging trucks. The spoked hub is the "wheel"
in this case.
    An automobile wheel has a rim, but it isn't called a rim. It's a
wheel because it has a center plate.

     5 x 4.5" pattern was used on Ford cars until mid-70s and on
Dodges. I think Chrysler still uses it. Many light utility/boat/camper
trailers use it.

      Dan (spent the '70s selling thousands of truck, earthmover and
auto wheels and brake parts)

       Hold the bus!  I forgot something!  International Harvester
half-ton trucks used 16" wheels on 5 x 4.5" patterns. Not split,
either. Rather narrow in the early years (4.5"), wider later on. Ideal
for trailer wheels. I've seen them on those trucks as late as the late
'60s, and they might have used them right up until they went out of
production in about '76. Older country junkyards (in farming areas)
should have some. Watch for the left-hand threads on the left-side
wheel nuts.
     I need to find some more myself, as the wheels I have aren't
that good and run a little eccentric. Didn't matter much in 1951 on a
truck that might never see pavement and couldn't go any faster than 45
mph.
       Why didn't I remember that? I spent three years restoring my
'51 International L-110 that I drive to work every day. Getting old
and forgetful, I suppose.

      Dan

I think this answers your question:
http://www.members.cox.net/completevalue/wheelpat.html  .
Best site I've found so far.  HTH, sdlomi2