http://www.jegs.com/i/Auto-Metal-Direct/106/425-4073/10002/-1
those are the outermost cab supports that the body mount sits under and the bolt goes up into this support. I'm not sure if you need the long one from front to rear or not.
If you order over a hundred dollars worth jegs ships it free and no oversized part charge on the cab pieces. jegs will ship to home for freight or summit they charge around $100 for truck freight, doors, hoods, bed sides, outer fenders ship truck freight, sometimes an outer fender won't go freight, and alot of the times now an inner fender doesn't.
http://www.jegs.com/i/Auto-Metal-Direct/106/405-4073-R/10002/-1
those pans are meant to drop in from the top and cover th emost area the others are replacments, they do not go up or out as far.
http://www.jegs.com/i/Auto-Metal-Direct/106/406-4073-L/10002/-1
those have your inner rocer on them, the outermost edge of the floor and such, depending on how bad the rust is in the lower lip of where the weatherstrip sits, how far back it goes this maybe the one you need.
http://www.jegs.com/i/Auto-Metal-Direct/106/440-4073-L/10002/-1
that one is basically the same piece but shorter, not as far back or forward.
http://www.jegs.com/i/Auto-Metal-Direct/106/450-4073-R/10002/-1
replacement style rocker, extends up the front pilar and up the rear.
http://www.jegs.com/i/Auto-Metal-Direct/106/402-4073-R/10002/-1
this is the area next to your foot, most of the time it's rotted, didn't see any inside pics but still here it is.
http://www.jegs.com/i/Auto-Metal-Direct/106/480-4073-2L/10002/-1
outer cab corner replacment type they do have some taller or wider depends on how bad yours ends up being
http://www.jegs.com/i/Key-Parts/576/0850-217L/10002/-1
these are the inner cab corners when you rip off the outer you'll most likely find this has rust as well.
xc_hide_links_from_guests_guests_error_hide_media
that is a good video on replacing all that stuff alot of parts check them out
keep in mind as others told me keep the cab on the frame or make a jig to keep it as it is before tear down and rewelding in new pieces. Also if you buy bigger patches then you need you can always cut them down and use only what you need.