Getting voltage spikes on ground, need some help

[1997XLTRollover]

As the title states, when I measure my grounds for voltage, mainly my block to body test, I'm getting a nice .02 volts, then bam it will jump to .4 or .7 or .8 even and then come back down. I then measured positive to a bolt on the block and get 14.1 volts which is exactly what my battery reads, but then every so often it will jump to 14.3 volts for a second and then come back down, my battery does not do this, this only happens on the block to positive battery post test. Could I have a bad block ground or is this normal or maybe my voltmeter has an issue?

 

[1997XLTRollover]

I really have a feeling whatever is causing this is causing all my problems that have me chasing my ass. Replaced gas tank, fuel pump, sending unit, battery, alternator, gauge cluster, ripped apart the entire evap and egr systems, resealed intake, replaced all 4 o2's etc. I think I'm getting false codes and I think my erratic gauges are also because of these small spikes in power.