When driving my C70 as I get towards the upper gears 5and 6 car gets noisy and lots of vibration.
anybody have any ideas ?

 

What comes to mind are the wheels or tires: have them balanced then see if that fixes the issue.

 

Tires tend to go through a harmonic with the suspension around 50 mph or something. That'll vary based on the spring rates. Vibration at speed is almost always tires, but it's pretty distinctive and you should have felt it sometime. it's identifiable. They can get out of round as well as out of balance. They do get noisy, but again, it sounds like tire noise, which can be howling, a whine, a roar.

Engine load, in my opinion, has no effect on tire noise and very little effect on the vibration. You have to think about that.