Radiator Cap:

If I'm right, a Ford Model A 1928-1929 will fit the 1928 Hudson radiator cap, which is 2-1/4-18 thread, but not the Ford Model A 1930-1931, which was one of the first to use the 4 lb pressure cap. I think its true that earlier years and all Essex are 2.0"-18, along with Ford Model T, all years. Someone please correct me if I'm wrong about anythink.

My question concerns the proper venting for the Hudson cap, should it decide to boil. Will the 28 Ford A rad cap really fit and is it OK for the car?

Gas Cap:

Now, the 1928 Hudson gas cap appears to be the same thread as the radiator cap. The only listing for the Ford gas cap I can find is on the Speedway motor site, and it does not specifically state the thread, but has the ID the same size as the 28 FORD A radiator ID. The male threads on the radiator and gas tank appear to be the same. The Ford gas cap is vented, which isn't necessary because the Hudson gas tank is vented under the rear passenger seat (Why would they do that?). Now, because of a parts list in a 27 Hudson manual, I get the feeling that there is intended to be a metal ring, rubber bushing, offset filler tube and gas cap, all of which, of course, have been relocated to the contents of the missing bucket. It does make sense to have a filler tube, otherwise it would be difficult to get the cap off because this is right next to the trunk rack.

What am I really looking for and where do I get them?