If your new cluster has an amp gauge just use the fat 10 gauge wire that is on the BATT terminal of the alternator to go from the alternator up to your new amp gauge then over to the batt terminal on the solenoid. You can then bypass your idiot light wire which is self explanatory. (No offense just thinking of Hudson engineers who introduced idiot lights in dash gauges in the first place.... - frown

If your new cluster has a volt meter... follow the directions for wiring in a volt meter which means one side of the meter will be for the hot or battery terminal and one will be for ground.
There you have it....
Randy