When I'm drivin one I get up to between 35 and 40 mph there is some vibration what could this b from

 

tires out of balance

 

Scream at the guy for messing up the speed balance. Check the lugs. On my 89, the rear tires were loose. If they are loose, have someone torque them down. If you have enemies in your neighbor hood, two locking lug nuts can slow them from loosing them.