CAUTION
The high voltage units work fine on older cameras - it is the newer ones that are vulnerable. The more electronics, the more vulnerable.
Mamiya advises caution - I have been specifically warned that my old Metz 202 is likely to damage my 645 Super or 645 Pro. The leaf shutters on my C330, however, are fine with the 202. The answer with respect to my Metz 60CT1 or 2 is, maybe.
A couple of years ago I was speaking with a camera technician who advised that one of the most common repair requests they get now is to fix either digital or small modern 35mm cameras with either a pc socket or hotshoe, that have been "fried" by using an older flash.
The damage can either be instantaneous, or cumulative.
Here is a link to a site that lists trigger voltages for a large number of flashes, and related recommendations:
trigger voltages
Please note that I haven't independently verified any of this.
Matt