First I'd like to say how much I'm enjoying this site.
Having driven my truck all last summer I had never had it over 60mph.The last weekend before parking for the winter,I drove it up to 65-70.There was a vibation.I'll list what work that was already done to it before I noticed it
front clip is 72 Nova -all parts ok
tires are new and balanced,wheels are not bent
drive shaft has been balanced
This vibration was not in the steering wheel it was in the seat.I think that indicates something in the back.Any ideas that I can look for would be great.Thanks, Boyd