As Rob said Macs only deals with commercial Fords. Just be thankful our UC have a lot of common Ford bits in them that ara available today. I wouldn't think they would have anyone there who can talk about Ford Military vehicles let alone one from a foreign country that is over 60years old. I would recommend you don't even bring it up. Just say your working on a vehicle that uses a Ford engine, transmission, rear diff and axle. if they ask tell them but dont expect them to know about the UC.
Whenever I have bought from Macs its always been through their website ordering. The new site with tons of pictures is great as you can really compare the parts listed to what you have in your hand.
There are a few really good Ford Flathead websites on the web that go into the differences and have basic parts breakdowns. Unfourtunalty my young memory has had a C.R.A.F.T.
moment and I dont know what they were called. A google search should bring them up for you.