'97 Yukon Guages floating

On my '97 Yukon the guages (not just fuel) are floating. Also the interior lights flicker at an idle. Alternator was replaced thinking the voltage regulator was going bad. Problem still persists. Is there any type of ground issues known of on theese trucks?

I have a 2001 yukon, similar issue, you drive along either in city or highway and the battery light comes on and engine shuts off. It then comes back on by itself and you continue driving. Checked battery connections, checked relays and fuses. Are there is shorting issues with the 2001 Yukon?