Thanks for everyone's comments.
The rims are new-style factory 124, with Michelin MXV4+ tires.
My mechanic was too busy to rotate or re-balance my tires. I re-checked the front end again and noticed loose wheel bearings. I tightened them, and there was a SMALL improvement.
More troubling, is I believe my transmission and/or driveshaft is a big part of the problem. The vibration becomes an issue after 60 MPH. Shifiting manually into 3rd gear makes a distinct improvement in the vibration - at 60-77 MPH. At 77 MPH, the car does feel a little wierd in third, but at 72, it's much more "solid" feeling. I think at 77, a resonance might occur from tranny to rest of car.
The tranny has known issues, including reproducable:
(1) rolls backward downhill on grade (easily)
(2) rotating driveshaft makes "klunk" noise. driveshaft havles themselves fit good - verified by my mechanic who "promises me" its the tranny
and intermittant occasional problem listed above, and a fast, harsh vibration (happened less than 5 times) when floorboarding car onto freewayat it reaches high RPM - makes me pull back off gas pedal - then goes away
I've replaced other suspension components in the past to cure various other problems including harsh intermitant vibration (front lower control arms), wind sensitivty/ride height (shocks, spring, subframe mounts), extra play in steering (worn components). Now its "tuned" into this. Most people don't seem to think driveline can cause steering wheel vibration, and I'm won't change the tranny specifically to reduce vibration (the vibration is annoying, but tolerable). I'm going to replace it because its starting to act up more frequently and I don't want to be stranded somewhere should it finally go, particularly with winter coming, and trips to family/friends for coming holidays.