There are two (at least) considerations. Many of the engines have the
"racing beat" underdrive pulley (mine did coming from Bruce), and I just did
the 'retrofit' to change the oil disable pellet under the pulley, because
the dimensions of the pulley were slightly different than standard Mazda
pulley so the pellet had to be a little longer. So -- the package has to
have a method of immobilizing the stator that will work with many different
front housings, be known to work (or supply) the correct oil disable pellet,
and align properly with the waterpump pulley.

Have I forgotten anything?
Bill Schertz
KIS Cruiser # 4045