Stereo & Electronics - Tach And Speedo

when i get on my car the tach starts bouncing all over the place along with the tach. whats up with this. my car also resests the trip when it dies or is shut off? any ideas as to what is happening. all of my grounds look good from what i can tell. i have done a head swap and im pretty sure everything is back on ok. but i was told there was supposed to be a ground strap from the passenger side head. i didnt see one. i was up and under the car today and didnt see it. any thoughts or ideas as too what my problems are. by the way i hope this is in the right place if not some one can please move it

thanks in advance
daniel

check the body grounds above the starter on the block.

will do, any other possible explanation