As long as the SL is one with a removable crown/steerer then yes. The later forks had press fit crown/steerer/upper legs, in which case you would have to swap out the whole upper unit for something more appropriate.
Maybe a stupid question, but is there a good way to distinguish based on external inspection? Best if I could tell the difference from a photograph (e.g., on eBay).
I'm guessing it would be easier to swap out a whole crown/steerer assembly than try to make a 1 1/8" crown work with a 1" headset (e.g., reduce the diameter of the steerer above the crown). I know a guy who can machine just about anything that is machinable. I doubt, however, that it would be a good idea to try to reduce a 1 1/8" steerer to 1". I weigh 145 lbs. and and not doing gonzo stuff at 57. But I also don't want to worry about a steering snapping if I hit a rock or catch a hard landing.
What's the wall thickness of the steerer on a 1 1/8" Judy SL?