I don't remember the gap spec., but I think that it is .034. The gap AND fresh copper cores did smoothe out the idle, no question. These engines do not have the super high energy igitions of many other cars of the eighties.
The broad electrode of the copper core plug with the SLIGHTLY opened up gap does smoothe the idle. If there was more ignition energy, you could probably open them to .050 or more and help immensely. I believe that this is an engine that would respond well to an aftermarket ignition system.
There have been a number of pro techs here that have recommended this gap setting and it worked for me.
Have a great day,