I swapped an older Copal shutter from a film lens recently, when the original needed to be repaired, and it worked fine. I am not sure how old it was, but it was old enough were the PC outlet was riveted in place, not screwed in place like modern shutters.
My concern was that the PC outlet would not sync with the back properly, but it did.
After getting the original shutter repaired, I did go back to using that one though. I did not use the lens with the older shutter on a professional job, but in studio and at my house, it worked fine.
I also read and heard that spacing of the lens in the shutter is not so much needed for making sure the front and back of the lens are spaced properly, but that the back of the lens is spaced correctly from the aperture blades. Apparently, refraction off of the blades can have a negative effect on the DoF if they are too close to the rear elements. Older shutter could have different tolerances; with this being said though, I still have yet to encounter a lens with shims in it.
(For the pixel peepers and techies, I know Alpa claims that Copel shutters could be off as much as 25 microns, which sounds like a lot. But when a company puts out a statement like this, that range is usually 6 standard deviations (3 SDs in each direction from the mean), which accounts for 99.8% of all variations. This means the SD is 4 microns. Now 68.2% of all variations are within just one SD from the mean, so chances are two shutters will not be any more then 8 microns off from each other. I doubt 8 microns is enough to make any noticeable difference.)
