It looks like your suspension is disassembled and floor pans have been removed so this may not apply..Weld in frame connectors (like the ones I bought from US car tool) need to be supported on suspension before any welding or is done. What I did was fit the frame connectors on a lift. Then with the car supported on jack stands under the front control arms and under the rear springs , i stitched welded the frame connectors in. Then I disassembled the car and finished welding it on the rotissary.