I have welded them in both ways, as a couple said if the drivetrain is stripped out a rotisserie is the way to go, much better welds and just easier all the way around. If the drive train is in it, then I do it on a lift, I weld the connectors in the back on the spring perches and use a floor jack to push the connectors against the floor, and then check the fit of the door gaps before I weld them to the torque boxes. Then I lift it up and finish welding on a rack. I like to put them in under tension with a jack loading them, it just seems to make the car stiffer.