Exposure may be difficult without a tracker. In the pre-digital days the common film speeds would get you up to ISO 400. I recall Kodak having a 1000 speed film for a while (it's gone now). But Milky Way images are often shot at, say, ISO 1600. ISO 800 would be perhaps a bit low (but I'm sure you could find examples.)
You have a limited amount of time before the rotation of the Earth makes the stars begin to grow trails.
On a full-frame (35mm) you'd divide 600 by the focal length of the lens -- and many people use 500 instead of 600 to be a bit more conservative. A wide lens is helpful for more time, but a low focal ratio lens might even be more important to allow the film to collect more light.
I haven't purchased film in a few years. I see numerous 800 ASA film choices. I see you can get 3200 ASA (Ilford Delta) B&W film. High ASA film is typically very grainy. Here's a flickr group pool with examples:
ILFORD DELTA 3200 Professional Black and White Film
Are you planning to do your own developing and printing (do you have access to a darkroom?) or are you planning to send it in for processing? I ask because Milky Way images (digital) typically have their histograms "stretched" to bring out detail that isn't so easily spotted in the native "out of the camera" exposure. There's a lot of post processing that goes into astrophotos. This is much easier to do in software then it is to do in a darkroom. But if you send it out to a lab then there's just going to do fairly straight printing and you won't have that level of control.