I found the problem!
The vibration was caused by the mount bolt for the control arms front bushing loosening slightly and over a period of time it elongated the hole in the frame.
This allowed the control arm to oscillate as much as an inch at the wheel.
Still contemplating the best way to repair it.

Tires can form flat and proud (bulge) spots only a wheel balance technician can surmise. Last time for a spin balance? Wheel balancing weight can come off through normal use or por application after the spin balance.

For flat spots and bulges, raise the corner and spin the tire slowly. The mesh nylon material the tire is made from, to which the rubber material secure, can fail and appear as bulges and dents in the side wall.

All for steering rack tie rods. Inside the collapsing bellows are the inner tie rods on the rack.

Yet not felt through the steering wheel, at all? Just through the car body as vibration on sweeping turns at 45 MPH+? Check the wheel balance weights, or, take the tires and wheel in for an inspect and wheel balance.

How old are the tires? What brand and model tire?

To large U-bolts secure the steering rack to the engine support member. The nuts (securing hardware can come loose in time. Raise the front or up on ramps, and check for torque.

Doubtful, yet how clean and the level of the power steering fluid? Any fluid leaks? Fluid contamination can manifest as strange, yet usually consistent symptoms. Though doubtful. Check the owner manual, yet you should use Ford "Type F" transmission fluid as power steering fluid.

As for strut mounts, it used to be we use Volvo PN 1272455 ONLY. Yet some turbobricks artciles suggest these suck as bad as Meyle/Febi/URO and so on.

Maybe SKF in the after market? Volvo OEM strut mounts PN 1272455 were / are made by Boge of Germany, using the FAG, what used to be SKF, ball bearing assembly.

Lettuce know.

cheers,

Dud MacDud - suffering the midwestern ills. St. Louis sucks.
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Before spending a lot of money and replacing the rack, I recommend eliminating all other possibilities first. Then, if you are pretty sure it is the rack go to a pro to confirm it. No sense in installing a new rack if it isn't needed...

Some thoughts popped into my head:

As necessary, rotate/balance tires and do a basic alignment check yourself. As the other poster said have you checked for tire damage and unusual wear?

You didn't mention bushings. Have you checked the control arm bushings?

You said the struts are old. What about the strut mounts? Totally worn out?

How many miles on your car?

Usually, the symptoms of a bad steering rack are power steering fluid leaks or stiffness when turning the wheel as if there is no power assist.

How old are your tires? Are they in good condition?