A Model B breather tube will fit a Model A engine. I put one on my grandson's 30 Tudor about a year ago. At the time all the suppliers were out of stock for the repos. I got an original from Sammy at Arizona Vintage.
Generally Ford "improved" the product line as he went along. The Model B oil filler would be one of these - if you can tolerate the slightly fatter appearance.
I have a caution note for those running the Model B oil breather pipe. The original caps are hard to find and expensive. I have lost 2 caps while cruising, so I now have a lanyard retaining them. I made the lanyard from a plastic coated fishing wire lead. no modification to the cap or breather tube are necessary.