Are your sure that’s even possible? According to Mobygames, 640×480 is the lowest you can go. And when I google this, I only get DF 1 results (which is running 320×200 anyway).
I think Windows 95 games are always 640×480 or higher. I would love to get a hack to run others like Half Life or Thief at 320×200 as well, but I think this won’t work, neither in Magic Dosbox, nor in the desktop version. Let alone the buggy Win95 graphics emulation in Dosbox in general. ?