I have a 1972 240z with a chevy 283 motor, mallory dual points distributor lately the tachometer has been jumping up and down then goes back to normal.
while driving today the car is now missing like its not running on all cylinders. Could this be just a bad plug or does it sound like it could be something with my distributer what should I be looking for.

 

It sounds like you might have a bad connection to your coil. This would explain the tach and miss issues.