Hi Colin
The Valve Covers off any Chevy from 38-54 basically with minor differences on where the oil filler tube is located. The Pat 11 and 12 have the oil filler tube at the front while the Pat 13 has filler located at the rear. Most if not all the civilian ones have a different filler hole located at the front. There are also civilian ones that have no filler in the valve cover and these are obviously good ones to convert for CMPs as with no holes you can put the filler in the proper location. I have seen various filler neck units used on CMPs the earlier ones look to be the section top of the civilian oil filler and breather that is found on the starter side of the block. The other style used on the later CMPs looks to be the same as the fuel filler and cap tube.
I'm collecting photos of the different valve covers I've seen or found on CMPs and posted them on my web site
http://www.canadianmilitarypattern.c...tingPage3.html
The covers are relatively plentiful in auto flea markets $10-25 USD so if you don't find one on your side of the Pond let me know and I'll look here.