Use hickory, forget about oak on Model T spokes... Oak is used and has been used on Artillery type spoke wheels, but only in large spokes, carriage, wagon, truck, etc.
The Model T wood spoke is very delicate in shape and size compared to wheels that use oak spokes. Oak has a larger grain, that is susceptible to splitting easy, just like a piece of firewood. The reason hickory takes a nice paint surface is from the fact that hickory is a fine grain hardwood that can be sanded very smooth. The fine grain imparts toughness to the hickory for use on light wheels that the light Ford uses. Same rationale for use of hickory on hammer, and axe handles and baseball bats.
Note the picture of the Ford hickory spokes end view showing the firm tight grain of the spoke taper end.
There have been spokes made of many woods, but don't risk it, use hickory for the Ford spoke.
