I did a bit more research and am tearing apart the "bad" one now to learn more about it.
I like that it actually uses "modern" seals rather than grooves to keep the oil in.
I have the milling ability here so opening that hole will be cake.
I'm wondering if I'll have to shorten the drive shaft as this trans is at least 2" longer than the sm420.
Thanks for all the help here!
Jeremy