I was just at the Walmart auto center tonite and I asked the manager 'who' makes Wal-Mart oil and he told me that it is refined at the Warren Oil Co. refineries.
I had never heard of them so I did a search and found this.
If the US military thinks it is good enough it should be for a Model A Ford! They also make AutoZone's brand of motor oils. Good stuff and should fit the bill. Cheap too. Check it out...........
http://www.warrenoil.com/