Looking to replace idiot light/speedo cluster with factory-type rally gauges in dash or do tach/speedo, and underdash Autometer gauges. Have good 160 mph original speedo but odometer frozen. I like the stacked gauges that came optional in the clock panel, too. So far finding prices $700 ++. Ouch. If I change from idiot lights to gauges, do I need to install new sending units? Anyone have anything? Other ideas?