starter relay on 1980
Thats battery cable and ground connections bad. Start at the bettery and make sure the connections on the battery are solid and the cables are not corroded inside the connectors. Then check the battery ground to frane connection, same deal. Then on to the starter, large battery cable connection there and the 2 fuse links on the battery cable on the starter, same deal, corrosion, burned connectors and the like. Then the main engine ground cable under the passenger side motor mount, same deal. Next, on the passenger side between the firewall and the head there is a connector that all the electrics run through, look for burned terminals.
See where that gets you







