Need Input on Suspension Fix, High speed wobble won't go away Options

[Bristol]

Looking for a little input here on a '72 914. Front wheels wobble quite a bit, starting at 60 MPH. I've had the car for five years and it has always done this to some extent, but it has gotten a lot worse lately. Over the years I've tried a few things to fix it - had front wheels balanced, changed front shocks, installed turbo tie rods, front wheel bearings, bump steer kit for steering rack (car is lowered). It's not bump steer though, it is a strong back and forth wobble in the steering wheel that gets the worst at 60 mph. Recently I even changed the wheels/tires thinking that the tires were maybe too old or rims bent.

I finally got sick of this (because it's gotten worse) and took the car down for the final fix - new A-arm bushings, new ball joints, totally rebuilt the steering rack with new bearings, new grease, and a nylon coupler between the rack and steering shaft like Tangerine Racing makes with it shortened to account for the rack spacer kit. I also fully inspected the front for any cracks or broken welds.

Despite all of my efforts the steering wheel still shakes badly. I plan on putting the car back in the shop again to change the rear trailing arm bushings and I will remove the new wheels to have them road force balanced. I am hoping that the wheels (which came from another car) are just out of balance/round as this would be an obvious cause that I have not checked (balanced the old wheels, but not the new ones). I may just have bad luck and replaced old wheels with really old tires with new wheels in an unknown state of balance that also just happened to be out of balance...

Is there anything else that I am missing that I should check? The only things I can think of that I have not touched are the rubber upper shock mounts, but they "look" okay to me and the bearing/bushing directly behind the steering wheel.

Kirk