I think the one assembly line  photo is the MH20.  I took the photo and blew it up 500% and counted the slats in the grille.  I counted 8 or 9.   The MH22 only had 6 slats not counting the top and bottom.   The 81 & 20 used the same grille but if the date on the photo is 11/47 that would make it too late to be an 81,  but production of the 20 ended in 1948 which would make it the right time frame.   The other photo of the assembly lines appears to be both 44's.  If you count the grille slats it appears there are 7 which would make it a 44 or 44-6.  They were both  being produced in 1947. 

Terry Kessel