They all fit the 727, 904, 833 and possibly a couple more less popular ones from the mid '60's through 1980 or so. They all fit the housing that's in the pic as well. Each gear should have the number of teeth molded into it.
If the 3 in the bottom right corner are 25-27 teeth or so, they will need a housing that looks the same but has the lesser numbers cast into it for proper "clocking"/installation.