Just to close this out. U joints were a little tired so I replaces them but still had the vibration. Looking closely I thought one of the rear tires looked a little odd. Trip to the tire shop revealed I was right. One of them had delaminated.

I am actually glad. The alternative looked like some potentially expensive transfer case work.

Ironically, a historical search will yield a thread a few years ago where I had a vibration on my SSC Civic that turned out to be a delaminated tire.

At least I found the failing u joints before they were a real problem. Balanced all the tires and now it's smooth like butter (with spare until I get the other replaced)