Hi Alex
Getting the body panels to line up on Pat 11 and 12 is a job. As Bob pointed out put all the bolts in loose then tighten things up. I found a trick using bolts a nut and washer to do the alignment it is a lot quicker than using the actual screws.
Take a look at photos on
http://canadianmilitarypattern.com/SheetMetalWork.html to see what and how did it.
Keep us posted your progress, going to be a great truck.
Cheers Phil