Takes a 50MT starter, long nose drive end housing, an adapter and a modified helical drive pinion.
Sorry I don't know all the actual parts involved as the 9G conversions rarely comes up.
The later 9G's (9418-up) had direct start but they also came with straight tooth flywheels while the pony versions are helical tooth.
Sale value of the pony motors is pretty iffy, depends on finding someone with a need.
Here's a couple of pictures from a conversion. Looking into the starter drive hole in the housing there is a casting bump that had to be ground away to receive the drive end housing nose.
This conversion was purchased from:
C & C Battery
Corpus Christy, Tex
1-800-531-1038 (Talk to Ken Sr. or Jr.)