I'd guess so....
Hi Bjørn,
I suspect it's not worth the trouble, and much depends on the case. To my understanding, many of these watches were sold with someone selecting a case and then a movement was fitted, obviously the case couldn't be too small (subject to some inor filing) but spacers or rings could down-size a somewhat larger case.
In all events, a calibre 66 was 18 ligne, and other 18 ligne movements --including calibre 57's-- in theory might fit, One would have to see what a watchmaker could do. Also, I can't tell for sure about height --if yours was an H7 it probably was 6.5mm high, but the cal. 66 came in 3 heights.
Given the cost, might not scrapping the case for its gold content and buying a replacement vintage pocket watch be easier and more economical? Many of the movements I see without cases have not been well treated.
Regards,
Michael