Happy to report I'm 90% sure it's sealing. I'm not at the test drive stage (new alternator isn't putting out a charge). But I filled the coolant and let the motor warm up a bit. No bubbles coming out of the resevior and only an acceptable amount of white smoke from the cold weather.
I also reused the mls gasket so I'm happy to report it's possible. First I drilled all the rivets. Then I cleaned every layer of it. Then I covered both sides of each layer with copper gasket spray and installed it.
I'll post back if it ends up leaking in the near future but I'm calling this a success so far.