Well, i know when i replaced the speedo cable on my 87 stang it took quite a bit of force(both are driven by cable so same thing). I ended up pulling as hard as i could and wiggle it some and it popped off, busted my knuckles in the process but it came off. It might be a little easier if you can take the dash trim off and pull the cluster to you some, i know it wont come out fully to just stare at it and see what to do, but it will give you some room to look at it and see what you can do. Just try to pull and wiggle a little bit and it should pop right off, its gonna take some finesse but it should work. hope this helps.
93ranger4x4