old car... rubber door/window seals start to shrink n harden... replacing these will improve nvh a lot... also plastic clips will start to break or go missing, new clips to lock it back in place will reduce rattling noises... engine mounting already mentioned and is very important to reduce vibration...

autofoam can increase chassis stiffness improves handling but will makes the ride harsher, and it will reduce some ringing noise... but imho complete waste of money... this was a fad 30+ years ago... if so good, auto makers would have incorporated into car liao...

when you respray whole car is the time to think about replacing rubber seals... do them together