the beauty rings around the headlights and the inner bulb holding ring is stainless on later models, earlier years it was chromed brass, i'm not 100% sure but i think they changed to stainless in 51. I have some of both kicking around, if you weight them side by side, the brass ones are heavier than the stainless ones.
also the brass ones will have a spot on the inside where it's obvious the electrical connection was made during the plating process.
i found both kinds of gas caps, stainless and just steel which may have been painted at one time.
the door lock key hole assembly is stainless on all my trucks 50-53
the trim on the rear taillight assembly is chrome on steel, i don't know if it was ever stainless, all mine are plated (poorly).
the trim around the park lights on the front is chrome on steel on my trucks, haven't found a stainless one of those, but doesn't mean it might not exist.
the bumper bolts are a stainless cap wrapped over the steel bolt head