[RyanAK]

Thanks for the suggestions. When I did the tires and wheels over the weekend, there wasn't any noticeable play, but we weren't specifically looking at the bearings and ball joints. Front axle u-joints are a contender, but there hasn't been anything to move them up the list.

I think dropping the front shaft is a good play. I'm leaning more and more towards driveshaft imbalance or the Double Cardan. I was looking through the service manual and the Cardan joint replacement/service looks like a sonuva*****. And there isn't really a reputable driveshaft place even somewhat local... If I drop the front shaft and that seems to solve the vibration, I wonder how cost effective it would be to replace the whole shaft/Cardan compared to labor and parts to rebuild/re-balance...

There's a guy in the Poconos that has stockpiled Squarebody parts and I think he has shafts available for something like $50. Maybe buy a front and rear and drop them off at a shop to rebuild?

In other news... the A/C compressor seized up and smoked the belt at the end of my 160 mile commute last night. At least that can wait until the spring!