65 mins would be tight IMHO but should be doable, provided you're on time and get off the inbound plane promptly. Cross your fingers on checked bags making it.

The good news is that YUL is not a huge airport, and the layout is pretty easy to navigate.

The bad news is that all Canadian airports seem to be experiencing staffing issues at the moment (particularly at customs and security) so YMMV definitely applies.

Good luck, hope you make it.