Sub-frame connectors

I think you should put that level on the nearest shelf, bring out the welder and get to it.

If you want to weld-in 40+ years of body-sag then just drive the car on a 4-post lift and weld them in.
If you want to remove most of the sag then put the car on jackstands near the transmission crossmember and front spring-eyes.

The choice is yours :)