brassbolt
The cab supports get welded to the cab floor and rocker panels.
Putting them on right is critical for proper cab/front clip alignment.
Bolter Woody "Czechman" has an excellent website and documented replacing those supports.
Might be worth your time to browse his web site and pick up some helpful tips
as stated above Temporally fasten them in place before final welding
Hopefully the person who installed the cab floors targeted the mount holes correctly
Good luck
