Intermittent starting issues

[brhulen]

97 4.6 Expy. No crank and no start. Sometimes it will start normally and when it does it cranks over just fine. Battery new and charged. When I turn key on, dash is totally dead and then after awhile I hear a click in the left dash area and warning lights come on. When I try to start I hear a click from the starter and dash goes completely dead again. After awhile the warning lights will come back on with same results. I suspect the GEM module as I have replaced it several times over the years. Some corrosion on ground cable but voltage is over 12 volts on battery but only 10.5 volts at lugs on firewall? So do you all think it is the battery cables as they are original.

 

[brhulen]

Edit: I pulled the wires off the starter and although they were clean I wire brushed them and put them back on with no change.
Next I jumped the starter solenoid and it would only click and then totally dead. Waited a few seconds and tried again with same results. Rechecked battery still at 12.2 volts.
What am I missing here?