Everybody's replies are great! I'll be taking a look this weekend and try to nail down the reason. I doubt it has anything to do with wheels and tires, since I just had those replaced or an alignment for that matter...
The vibrating noise sounds like it emanating from the firewall area and/or drive shaft area. Its just odd that it only occurs going faster than 70 MPH.
Hello fellow A-body enthusiasts,
I recently purchased a 1971 Dodge Dart Swinger with a 318 swap (original 225 inline six) and original 904 transmission. Every time I drive in excess of 65-70 MPH, the car starts making this humming, vibrating noise. I recently put all new tires and had an...