http://www.gomog.com/allmorgan/4~4%20Diagram%20for%20Morgan%20Dash%201800%20Focus.pdf

Assuming this is the correct wiring diagram and that the same fault is causing both problems: all of the instruments are fed from the same wire (green) that goes back into the loom at the top of the diagram. You'll need to trace this back to the fuse. Then test for power at every connection until you find the problem.

1972 4/4 2 Seater