Mike,
The basic trim rings are all interchangeable but there are are some minor finishing differences in the KWM2 ring, as I recall. For example, as far as I know all the KWM series had the quick-lock fasteners for the cabinet lid and the associated holes in the trim ring. The 32S-3, or at least my own and the ones I'm familiar with, do not have the lid fasteners. But apart from the extra invisible holes, you should be able to swap the the KWM ring into the 32S-3. A fair amount of Collins trim swapping goes on across the S-line, if only to replace yellowing plastic trims in later equipment with the metal rings from earlier radios. There are treatments available to restore the plastic if you're keen but I prefer the metal rings.
73, Peter.