Hey TPB,
I am working on a 58. Mine had a lot of rust hidden by bondo and tar etc. Here is a list of places to check out besides the cab corners that i had to fix or replace:
rocker panels
steps
lower front fenders where they meet the door
pillar pockets inner and outer
hinge plates
front bed panel
tailgate
front fenders in corners
bedside panel stake pockets
toe boards next to kick panel covers

Most of these issues can be dealt with patch panels and alot of the smaller areas can be cut out and you can fabricate pieces to put in.

If you blast the truck be prepared to find lots of holes and damage and keep in mind that once you do this it is harder to sell than as it is now.

I found these articles really helpful:
http://www.classictrucks.com/tech/0208ct_replacing_doorsills_rocker_panels/index.html

http://www.brotherstrucks.com/techa...%20CORNER%20PATCH%20PANEL%20INSTALLATION

Good luck!! its fun
brian