I have a 73 charger that have a bad vibration at about 6o mph I have replaced rear tires after being told by two places that one of my rear tires had a flat spot on it, when I say a vibration I really mean a vibration that can be felt more when you get off the gas,I have what looks like some kind of a balancer on the rear of the trans that have two bolts that mounts to the trans, I noticed that the two rubber bushens are just about gone ,could this be my problem? I plan to check weight on the convertor and the balancer on the engine. what else could it be? also I will be checking the drive shaft weights. The engine is a 360 NEED HELP.