There are the illumination bulbs, and the indicator bulbs. Are you talking about none of them working? Or just the illumination?
The Blue w/red wire powers all of them from the light switch, so when you were checking were you sure the light switch was on to at least the first click and the rheostat is turned all the way up?
You should check each bulb to make sure it's good. They can go out one at a time over a long period until none of them work.
Next would be the fuse. It's (if I remember correctly) the smallest one in the fuse panel. Pull that out (carefully) and clean the contacts. Put it back in and check again. Should be power only when the light switch is on and the rheostat turned up.
For the gauges, it sounds like your regulator is working. A bit high of a reading in fact, but then the gauges should just read high. You say they're not reading at all?
As was suggested, a good ground wire from the cluster to the dash, then another from the dash to the body would be a good idea.
Then you should check the sending units. One easy way to test that the wires are good is to temporarily ground the connectors at the sender. If the gauge pegs to the high end when you turn the key on, then your sending unit(s) is bad.
If it does not peg, then either the wire is bad, the gauge itself is bad, or the ground is bad.
When you measured the output voltage of the regulator did you verify that the power was getting to the gauges?
Paul