gauges custom 880

I am working on 64 custom 880 the gauges dance back and forth. Was wondering anybody has seen this problem or may have wiring diagram on car? Also was wondering if the 5 volt refernce is built in to the gas gauges? Cause the other gauges share the red wire from gas gauges. Thanks for any help.

http://www.mymopar.com/index.php?pid=26

Thanks a whole lot. Turned out to be a bad fuel gauge. Thanks again.