Chances are all you need is a standard 1 1/8" EC cup headset.
The photos/info don't help too much, a side view of the headtube, rather than top would be more useful, and the date range of the bike is a little vague.
If you do know the specifics of your bike, you could always look up old catalogues which will often include exact specs, or use a tool like the SHIS
Everything You Need To Know About Headsets - Cane Creek
CaneCreek SHIS Poster_v20 (problemsolversbike.com)