Shouldn't be that bad to narrow down.
Light comes on if there is a path to ground.
The handbrake switch you can see pretty easily under the dash. Make sure that's not lose or the wire's insulation chafing away.
The warning switch is in the distribution block on the frame rail. A single wire comes up along the inner fender and is wrapped into the harness.
The safety switch works the same way on all variations of the distribution block.
It's explained here: 1970 Brake Hydraulics page 9, Chrysler Master Technicians Service Conference
