yes, they had been replaced at same time, 1500 miles ago.  I should have mentioned that

Both of these were done

Warped discs or rust buildup behind or on the pad.

Pull the front wheels and check for a pad shaped lump of corrosion and use a DTI to check for runout.

Have soft (flex) hoses been replaced in all this?

front end shuddering on hard braking at 60 mph, not noticeable at low speed. Feels like warped rotors.
No shaking unless brakes applied, so wheels and tires are okay.
emergency brake usage while moving does not elicit symptoms so rear drums not thought to be the problem.

feels like warped rotors but rotors, pads, calipers, cones, upper control arms, shocks replaced as preventative maintenance only 1500 miles ago and all was well until recently.
No ham-fisted lug nut tightening. No racing.
Dial runout shows both rotors are good. Changing pads no help.

Grasping at straws here  - Anyone ever seen a 'fluttering" limiter ("proportioning") valve cause this?
This is the brake hydraulic valve that sits below the master cylinder.

Suspension seems okay. At least nothing is "jerkable."  Not sure about subframe or motor mounts.
Could either of them, if worn, accentuate a minor warp in the rotor ?

Thanks