UPDATE#2:
Found the problem. Internal short with the stock AM/FM radio. Internally the radio light is grounded. It's not worth the trouble to pull the radio and tear it apart to replace a stupid light. I never use it anyway. At least I've got my gauges back and everything else seems to work well. Interesting problem, huh?
Thanks

Does anyone out there have the internal layout of the headlight switch for a 71 B-body. I'm having a problem with no power to the instrument panel lights and I think it might be in the switch. Replacing the switch is a HUGH undertaking and I'd like to be more sure that the problem is in the switch before tearing apart the instrument panel to get to it(you know, lowering the steering column, removing the A/C control, radio, console, etc.)
Thanks

I dont have what you need but you do know the dash lites go through the resister on the headlite switch that changes the voltage to the lites when turning the switch ? The switch also has an internal circuit breaker but its for the headlites and no lites would work if the internal circuit breaker was bad. I have seen the contact for the dash lites that rides on the resister get corosion on it and cause dash lites not to work. Also dont forget when the power leaves the headlite switch for the dash lites it goes through the dash lite fuse in the fuse box. RonRon

there is a fuse on fuse panel which is exclusivelly for dash dimmed lights. One of the top ones.

Although I have seen more fails due the mentioned corrosion on rheostat than the fuse itself

Thanks for getting back. I appreciate the help.
I've narrowed down the problem to no voltage at the 5A fuse from pin 1 on the headlight switch. All the other pins seem to be doing what they're supposed to be doing (everything else works) but pin 1 looks like the feed for the 5A fuse that protects the lights on the dash and there's no power to that fuse. There initially was power there but it blew the fuse and its replacement. After that it just simply didn't have power at the fuse. My question is: Is there a condition where just pin 1 fails internally? Do my problems sound like a classic failed headlight switch? Is this a common failure on these switches?
Thanks
UPDATE
I think I found part of the problem by disconnecting the connector that feeds the turn signal flasher and radio. Disconnecting this connector kept the fuse from blowing when the light switch was in the parking light mode. Dash lights work. Even the turn signals work so that connector must not feed the flasher even if the book says it does. Wonder what it really feeds? Interesting trade off.

do you have parking lights?

originally the source for dash lights comes first from parking lights ( which is fuse protected too from batt source ).

Once it gets the power from parking lights source, goes to dash light fuse, then it spreads to all the dash