Shudder in High RPM's
 

1980 Camaro w/ 229 V6. under the hood in high rpm's sounds fine. In the car parked or driving, you can hear a shudder or vibration in high rpm's. You can feel in the stick as well. Car has 35k original and required quite a bit of tune up. cap coil rotor plugs wires filters fluids all done except Manual 3 spd trans.
Could this be a trans issue? Has HEI so I don't believe timing is issue... totally dogs in the high end.. Anyadvice out there