1967 Other Pontiac Models '67 GTO has noise under hood

I am the original owner of a classic 1967 GTO. It has a 400 cu. In. Engine with a factory 2bbl carb. No A/C. Recently, it developed an intermittent grinding sound from under the hood. It also sounds like something metal is rubbing against something. I thought it might be wheel bearings or spindle damage. All checked out OK. I replaced the old water pump since it seem to wobble slightly on its shaft. After removing it, I discovered that the bearings were really noisy and I thought I had found the source of my problem. Not so. The water pump did not make a difference as the noise continued. The noise is evident on straightaways even at slow speeds. It does not get louder with more speed or rpms. It is not a constant sound but comes briefly and then goes away. I checked the alternator at a parts place and it checked out fine. I am running out of things to check that have bearings that might be causing the noise. The only item left that is belt driven is the power steering pump. It is the original pump and the car has 121,000 miles. Could I check it by removing the ps belt and driving the car with unassisted steering? Would I hurt anything by doing this? If the noise is not evident, then it must be the ps pump. Any other suggestions to determine the location of the sound or defective part? Needless to say, this car has been meticulously maintained.