Operator/window open
You know, I was looking at the 39-326 before I wrote my initial response, and to be honest I ruled it out because of the design of the sill mount plate. Yours looks smaller, which also indicates an overall smaller base. My worry was that the 39-326 wouldn't fit in the cutout of your sill trim, so I decided not to mention it.
Basically, the 39-326 has a very uniquely designed base measuring approximately 4-5/8" wide (it might actually be a hair wider; it was hard to get an accurate measurement due to the contour of the cover). Does yours match that size and style? If not, then I don't believe it will work.
If that's the situation we're in, then you can still get our 39-171 and 39-172 to work. There's a good chance that they'll work as-is without any alterations, but even if you run into trouble there are two fixes to make up for the difference in link arm size.
-You can adjust the position of the bracket to which the arm attaches. What I mean by that is that you could theoretically move it over on the sash to make up the difference in size. This will require drilling new holes for it to screw into.
-You could swap the link arms out. This is done by drilling out the link arms on both operators, then installing the old arm on the new operator hammering on our 62-014 rivet over a metal plate.
Let me know what you think of these potential solutions, or if you have any questions.