Yes Ian you are right, I also posted a reply to this tread that was lost.
Anyway Steve, as Ian suggested try
www.vehiclesofvictory.com and go to "Parts For Sale", in the bottom of that one you will find a post from Richard Privat. He got a lot of used/take out parts for Chevy's and can probably help you with some of the parts you are looking for. I bought the frame parts for the winch and a winch for my Chevy from him.
For the clutch head screws you could try Jim Carters site
http://oldchevytrucks.biz/p/1934_194...ge.php?page=t1 and search for clutch head. Then you should get up both the screws and the tools for them. He is concentrating on parts for the civilian Chevy's, but a lot of these go on the military versions as well.
Good luck with your project Steve.
The roof mounted periscope was also used on the Chevy 1 1/2 ton 4x4 Telephone maintenance truck K43.
Geir