That is the really correct answer and if you brace the cab, you want to have it sitting level first. The problem with doing the repair with the cab off is that there are no references to the rest of the structures.

1951 GMC 1 Ton Flatbed -- It is finally on the road and what a great time I have driving it!
1951 1 Ton Completed

My Chevy Master 4 Door is on the Road!