Ok I now have found the proper place to post this.
I took on a project that some one else restored and now I maintain. It is a 1954 3100 short box.
When I first saw it I noticed that the rear wheels were not centered in the wheel well opening. They set rearward of center about 3 to 5 inches. The owner had never noticed it until I pointed it out. It was obvious to me and the restorer whom I don't know nor have ever met. Why he didn't fix it IDK!
Anyway the owner let it set too long and the brakes were leaking fluid. I pulled the wheels and ordered 4 wheel cyl's. and a master cyl.. When I went to install the rear wheel cyl's., the ones I ordered were different than the ones on the truck. I had to take one to the parts house and match it up by visual lookup. The cyl.'s we now have show to fit a GMC and not a Chevy. (according to the parts book). Here is a picture of the wheel cyl. installed. http://i1070.photobucket.com/albums/u497/toyvo75/100_7234_zpsxymevod0.jpg
Here is a picture of the wheel opening with a chalk line showing center. http://i1070.photobucket.com/albums/u497/toyvo75/100_7209_zpsyihsyvxd.jpg
Here is a picture of the front of the drive shaft tube showing the amount of available travel at the slip yoke. (about 5 inches)http://i1070.photobucket.com/albums/u497/toyvo75/100_7235_zpshnzvbz2a.jpg
I have come to the conclusion that the springs have been installed backwards and this is causing 4-5 inches of being off center. Picture of rear diff and front of tube. http://i1070.photobucket.com/albums/u497/toyvo75/100_7226_zpsvqqjw4jx.jpg http://i1070.photobucket.com/albums/u497/toyvo75/100_7225_zpssgvdbtkd.jpg http://i1070.photobucket.com/albums/u497/toyvo75/100_7223_zpskasubdfc.jpg
A few pics. of the truck and the trailer is was built to pull. http://i1070.photobucket.com/albums/u497/toyvo75/100_7212_zpshyslo4qj.jpg http://i1070.photobucket.com/albums/u497/toyvo75/100_7211_zps52vg84zi.jpg http://i1070.photobucket.com/albums/u497/toyvo75/100_7217_zpsqj3mkje6.jpg.
http://i1070.photobucket.com/albums/u497/toyvo75/1954Airstream/100_7227_zpsdaf3urbq.jpg
http://i1070.photobucket.com/albums/u497/toyvo75/1954Airstream/100_7229_zpsyfzcgavn.jpg

I didn't do it, no one saw me do it, you can't prove anything! "Bart Simpson"