Thanks a lot everyone, I really appreciate the information.
I put new ones in about ten years ago but I think the trip to California and back with the wheels tied down in the trailer did them in.
When we took the car out of the trailer in Monterey last year several of my Heims joints were squeaking badly. When I first drove the car I definitely heard a rotational squeaking from the left front for a few seconds then it never returned. All the Heims noises went away except one.
I had to take the right rear lower A-arm joint loose and lubricate it. It was worn very slightly after 64,000 miles. It was really hard to find, I put the car on my lift and you could feel the shock from the binding throughout the rear suspension. I had a friend come over and while he pulled the car up and down I was able to find it. The "crack" sound was strongest in the A-arm joint. Easy fix.
I remember that when I bought the bearings last time I was told they were Mustang parts but I see on the internet that they are very common Ford parts from a number of different products in the 60s and 70s. I did not remember that they had numbers on them.
Thanks a lot, the wheels are up and I definitely need bearings on both sides, absolutely no effect on steering, just a grinding noise when moving, detectable at about 30mph.
All the best,
Dick Ruzzin