I have one of these stashed away for a someday build too and will definately be building as electric. Bob Benjamin has a build series on his website for an electrified SR9:
Building the Stinson SR-9 Archives - Bob Benjamin's Master's Workshop
He does not go into too much detail about the motor selection, but it is a good writeup on the basic construction of the plane. In his flight report, he states that he is using an "AXI 5230-24 motor running on 8S", and he does come up with a clever split cowl design to access the batteries (you can find that in one of the build posts, but not sure which one).
Post a build thread when you get started. Maybe seeing another Stinson will help get me motivated to start my own!