What would cause all the lights to pulsate on a when engine is running on a 1985 corvette?
Generally this is due to corroded/ old/ poor ground connections.
Your engine, frame, battery, and electrical grounds must have good
clean connections especially on a fiberglass car. I suggest you
purchase some grounding straps and attach them to clean points
between these areas( You can't have too many). Sand off and rust or
old paint; this should solve the problem. A defective alternator
can do the same.