Ok iam installing 3 gauges and my tach..can i hook up all of the power wires together and connect it to one power source?

 

Yes. Combine the ground wires and find a good screw or bolt under the dash (in chassis metal) to attach them to. Combine the +12V wires and run them to the "IGN" terminal in the fuse block at the end of the dash. You might want to keep the +12V for the lights separate, and run them to the fuse that powers the dash lights, or to the output of the headlight switch or the dash light dimmer switch. That way, the gauges only light up when your lights are on, and you can dim them if you want to.