[Coupeguy2001]

I have a Kimbridge front frame stub in my 57. It is essentially a custom G body geometry front frame stub.
The springs I used are QA1 coilovers, and tubular upper control arms.
I got the coil-overs from speedway motors in Lincoln Nebraska. They are 550's

I also used 1996 Impala SS wheels, with 255/50/17 tires.
I had a heck of a time finding springs that would raise the truck up enough to be drive height, and finally went with the QA1's.
The problem is that G bodys never came out with big block engines.
Stock springs are not up to the task if the vehicle weighs more than a stock G body with a small block.
but I would bet that your springs haven't been heated, they are just not strong enough to raise the truck up to a driveable height.

What I did was use dirt track rotors with different bearings to get the 5 on 5 lug pattern to match the 72 rear axle. They are available from Speedway as well.
I also used the tall ball joints in the upper control arms to control the wheel arc as it raises and lowers the spindle when you go over bumps or dive into a rut.
I have not had any problems since I used Moog parts, because some auto parts ball joints etc. are made in various countries, and various quality exists.