OK ,that explains why "6V and 12V parts can be interchanged" is incorrect. The drive splines on the 6V asrmature are definitely straight, so neither the 6V drive gear nor the armature can be installed in the other housing individually. It would be possible to use a 12V arnature AND drive in a 6V housing to accomodate a 168 tooth flywheel. We did use 6V armatures and field coils with special gear drives to make "super torque" starters for small block Chevy racing engines, back before the planetary gear Mitsubishi starters came along.
Jerry

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