77 vette no dash/tail lights

have a 77 vette that th tail and dash lights stopped working
changed switch and still same thing
does anyone have any ideas or a wiring diagram for this car?
if so it would be greatly appreciated
thanx in advance

I've seen several 30+ year old bodies which have marginal connections at the bulkhead connector (C100) right on the firewall. You can at least peel away the duct seal, remove the screw, open the connector, and look for damage.