[A bones]

For me, i'd like to start out on a post ( 1 or 2 ) lift. Watching the tire treads spin, for wiggle or bump from the road's angle. ( looking as they slow for signs of major imbalance [ pendulum ]

I would NOTT assume that the performance of the 'operation' is the cause.

While under the car, test for any looseness. Having a helper at the wheel is big.
Shake shake Rock rock Push pull, Wiggle wiggle. Everything from the tire to the steering wheel.

Too much loose in any one place is a problem. Remember though, Some here, some there,... And there adds up to the same problem.

Yes 1931 Flamingo I forgot to mention to rule out the balance issue. At times though we get hung on a specific point and forget to step away and see the big picture.

Verify king pins, shackles, and spring U bolts conditions. If an anti-sway bar is employed, look for missing, loose parts or decayed rubber.

Always a caution, extended period of wobble on the road will degrade your joints. Don't let it, Travel below fifty. Good Luck.

P.S. Your Coupe is more than Cool It's beautiful