I Like my two Tanaka's, however, they are practically Identicall, so i could be talked into parting, I think there miught also be a slightly newer Tanaka straight shaft somwhere, I'll get some pictures up.
The Ryoby extensions would be very interesting to me as I do have a split shaft, or, if you want them, I can give you a ryobi split shaft, or adapt another engine onto a ryobi split shaft for you.
In fact, my later tanaka engine might go well onto a Ryobi Scrub Hornet shaft I have, its a split shaft, Bullhorns with straght shaft end on, I'll have a look into that idea, let you know.