cruising in 4th at approximately 70-75mph the tach needle will read between 3000-3500rpm and will start to jump erratically any suggestion stock ignition system. wondering if possible bad ground or faulty distributor any suggestions

 

see if your coil wires are close to any of the spark plug wires. that can do it.

 

no i checkeds that already. made sure to do that in the first place thanks for the thought though. i think i am going to double check the wires and there resistance. what's really wierd is that the fast i go and the higher the rpm such as 3500-5000rpm the needle twitches even more. i don't know if its even related but some times the temp guage will twitch slightly too