My 1968 Plymouth Sport fury

Hi guys I have a few questions for guys that have a car like mine I have a weird shake / vibration that comes in at 70 mph is this normal I've replaced everything under the sun if you name it I've replaced it can't figure it out all the front suspension is brand new universal joints are all brand new I can't pin it down but also I'm looking for seats bucket seats and I'm looking for console and shifter linkage and rods if anybody can help me be gratefully...

My 1968 Plymouth Sport fury