When I was working on the engine for my `41 pattern 12 I ran into the same thing there are some notes pictures on my web page
http://www.canadianmilitarypattern.c...Page%20Two.htm . You can make almost any of the dipsticks work by changing the length of the side tube that it fits into. A lot will depend on if you have the orginal deep sump or a later shallow sump. You can see by the pictures on my web site that with the deep sump most of the oil is actually down in the bottom sump when the engine is not running. Point to watch for if you are going to try and correct lenght of dipstick is that the splash lubrication system holds a lot of oil up in the troughts. I'll check some of my early civilian parts books and see if there is a civilian one that would match. Need to confirm though that you are working with the deep sump.