When to weld in subframes.

A 460 will flex about anything. I'd go ahead and weld them in empty so you are not locking in any loaded spung condition. The whole connector install deal is pretty overblown. I usually put stands under the rear A arm mounts on the K member and under the shock tabs on the rear axle. That way the chassis can 'rest' on the rear springs similiar to how it'll sit on the road. Haven't had any problems in dang near 80 installs.

Jamie

If it was my choice I would wait but I guess the biggest thing is as long as the car is sitting level you should be fine. But most say the suspension should be loaded and all four tires on the ground. I did mine with a pit in a garage, the other option would be a drive on lift.