Time to rebuild?

Bill, I already adjusted the idle mixture warm, and won't mess with it now. It idles pretty well warm, and I'm not sure what would be different cold other than the choke. The thing is it used to idle just fine cold, until recently. It didn't get worse after anything I did, just on its own.

Dan, thanks for the tip on the electric choke upgrade. (But I still don't think the choke assist is involved in this specific problem unless it's somehow heating when it shouldn't.)

Manual chokes were still around in the 70's. My 1971 Volvo had one. The setting was like this: you pull it out to start, push it halfway in when you pass the stoplight, and the rest of the way in as you're entering the highway. :)