I bought a 1977 Nova and it had shaking issues so I was told my rims were no good so I bought new rims, balanced the tires, had a front end alignment and replaced the U-Joints. It is now pretty smooth until I hit about 50 mph and it will shake a little but in a pattern where it will shake a bit and stop for a second or two and then shake again and so on. Any suggestions on what else I have to look at to correct this annoying problem. The car is very solid and handles easily but I want to really enjoy driving it this summer so any help is greatly appreciated! Thanks!