Frame Connectors - install question

It doesnt make a **** whether or not theres suspension under it or weight on it. What matters is that you place your jack stands evenly at both ends, and use bubble levels in 4 spots and use shim stock between the stands and framerails to make sure the car is level before you weld these things in. If it's a convertible you temporary weld bracing front to back near the top of the door openings before doing the connectors or and floor replacement.

If you wanna make sure its square on jack stands, get 4 spirit levels. Mount one on each rocker in the door openings facing fore and aft with sill plates removed. Put one across the rear shock tower area top of transition pan facing side to side and one across the upper radiator support on the small ledge on the support at the opening facing the radiator. May have to loosen up the radiator to get the level in there. You shim the jack stands with thin steel strips to get the final level on all 4 axis, then weld in those bad boys and dont look back.