So I am having my subframes installed on my 98 in my sig by a friend of mine who welds. Should the car be evenly supported by the frame at the time of the welding? Or should the weight of the car be supported by the wheels/suspension?

 

The vehicle's weight should be on the tires (the suspension should be loaded).

 

resting on the wheels.

don't risk tweaking the frame

 

And doesn't everything have to be level? Just making sure

 

where to put the load? I'd go with your mother's eye personally... ha!

ok seriously... on the tires, or in the rear, on the axle. it should be close to level, but doesnt have to be perfect.