My advice would be look at the wiring diagrams, unplug the distributor, metering head, etc working your way thru all the ignition and fuel side removing one plug at a time and check the power supplys and earths for each component. More than likely that something has been disturbed while you had the dash out? That's just what I would do, before you go to all that hassle, how good is your distributor? as they have a habit of going on RST's, I had to replace mine twice, ended up just buying a brand new one from Lucas or whatever it is they call themselves these days? If you have access to a known dizzy that works swap them and see if that sorts it?