Ask Omega and they will tell you it can't be done. But it can be, and has been, done. I personally have read the posts (and seen the photos) of other WUSOF members who did this modification (as well as those with Speedy bracelets who also needed different saddle links). I know the information is in one of the threads on WUSOF dealing with these clasps. I just don't know which thread, or which post. But I'm not the one with the older watch, so I'm not going to spend hours searching for that information. I can only tell you that it is there for the finding.
If you really don't want to retrofit the new clasp to your Gen1 PO, then keep asking Omega if it is possible.