As for the evaporation experiment, You need to take into consideration the effects of air flowing on or through oil.It does get warm near the engine.This thins the oil.
.Get a cup of warm oil and blow on it or use a straw to blow into it.Make sure no one is standing opposite of you very close.(remember that the vacuum of the engine has more force than you can blow.
.As for the element material in the oil-bath filter,oil does creep up into the fibers,not much but more than a paper or synthetic element.
.Oil-bath air cleaners are correct for the restoration however, I would leave it dry and install it on the truck for looks after I arrived at a show or meet.

There is enough good in the worst of us and enough bad in the best of us that it does not behoove any of us to criticize the rest of us.
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Be yourself. If you are ever lost, It will be much easier to find yourself if you know who you are!