I think you may have the same wheel cylinders as mine they are still available from Napa.
The fronts should be 1 1/4 diameter
Rears 1 1/2 diameter.
If you look at your originals the size should be stamped on the side of the wheel cylinde.

This is the front http://www.napaonline.com/Catalog/CatalogItemDetail.aspx?R=UBP3406_0220763891

This is the rear http://www.napaonline.com/Catalog/CatalogItemDetail.aspx?R=UBP3677_0220763782

If you click on buyers guide, on page 3 it says they fit your truck..

This is the master that fits my truck http://www.napaonline.com/Catalog/CatalogItemDetail.aspx?R=NMAM661_0332938227
The bore size on this one is 1.5, has an outlet on each side and a port for the brake light switch on the end.

I just did some extensive research over the last few days, im also in the process of hunting down all the brake parts for my truck as well.

Are there any numbers on your old master cylinder?

Last edited by JeffL; 02/24/2013 5:00 PM.