Sitting in my parts bin is a genuine Diemaco 1:7" gov't style barrel with front sight assembly in the original wrapping acquired many moons ago.  I would like to mate it to a real, non-M4, Diemaco upper with the Canadian-spec rail...not the Picatinny version.  Black Rifle II states that the rail height (and width) is different between the Canadian uppers and the US version.  The Canadian rail is slightly lower than the US rail, obviating the need for an "F" marked front sight post.  My Diemaco barrel is not marked with a "F".

I know that I could buy a higher sight post from Bushmaster, get a US Picatinny-spec upper, and simplify my life....but then it wouldn't be a genuine Diemaco upper receiver.

I also have the neat polymer rear sight that the Canadians use in front of the ELCAN as well, so the finished version would indeed be unique.

Any leads or thoughts would be appreciated.

Wild @$$ guess.....

Call Colt.   Their parts # is 1-800-426-8001.  

Another option would be to contact SAW.  They don't have them listed but they seem to be able to get just about anything from Colt.   On the plus side, if you buy the receiver and other parts from them, and send them your barrel I'm sure they'll assemble it for you for free.  

https://www.sawlesales.com

In either case don't expect the upper to be cheap.  However, it will definitely be unique (at least in the US).    Do send pics if/when you put it together.  

If you want to make it a real CF clone, you might want to consdier the Vortex G6A2, which has been adopted for their C-8's and is in the latest Diemaco catalog.   The Vortex was adopted by the CF jsut a coupel of months ago.