Here is a previous string on oil, is one of those topics where there are multiple opinions. There are a lot more strings if you do a search.
https://www.fordbarn.com/forum/showt...el+Mystery+oil
Rotella T4 has some Zinc in it if concerned about a need Zinc. I use it even though personally I do not think Zinc is necessary after motor break in on Model As. The amount of Zinc in the current T4 formulation seems to be fuzzy. I have read that too much Zinc is not a good thing, more is not better. You need to know how much is in your oil, and add only what needed. Too much can damage metal over time.
My view is that the Model A does not need Zinc, the A motor is low reving, teh valve springs are relatively weak and do not create as much force on the Model SAA tappets/valves Cam.
More important than type of oil is to change it frequently. It helps to keep contaminants from getting into the lower end bearings. An alternative is to add an oil filter. Even if my A had a oil filter I would still change it frequently, oil is cheaper than an engine rebuild.