Gone:
Welcome to TBN. /forums/images/graemlins/smile.gif I agree with the others that you have one heck of a neighbor there. Please let me know if the property on the other side of him ever comes up for sale!
Nice drawing, and nice repair. I'm not a mechanical engineer or metallurgist, but I did get a great night's sleep last night, and I have a feeling that repair is going to last. In fact, it might even be stronger than the original, when you consider the total surface area that those bolts are grabbing onto. The setup you've got now reminds me of how a u-joint gets secured into a yoke, with caps and bolts. Granted, the force vectors are much different, with yours being basically longitudinal; but it's going to take quite a bit of force to pull those bolts straight out of those tapped threads.
I'd just make sure the threads are as deep as you can make them. Maybe try to find out how much meat you have to work with before/if you were to deepen the holes, so you don't drill right into the gearcase; but even if that were to happen, seems to me you could still seal the oil in just fine. (The resultant metal chips in the gearcase would be far from ideal, but probably wouldn't end up doing any damage, and would probably come out with the next oil change). Plus, this might be moot anyway - you might have plenty of room.
Oh, one more thing - you might want to considering vee-ing out the fracture lines and arc welding them with Ni-rod, just to help take some of the load off the bolts . It's pretty amazing stuff, and although cast iron is notoriously tough to weld, I have had great success with Ni (nickel alloy)-rod. Pre-heating is always good for penetration, but you don't have to be too particular about the cooling process, in my experience. If you can pack sand around the fresh weld somehow to slow down the cooling, so much the better, but it's pretty forgiving stuff. I'd give it a go though, that repair can use all the strength it can get. If those threads did strip out, things would start to get a little more complicated and "dicey". (Heli-coils, bigger bolts .... I'd hate to see you have to go there - and let's not even think about replacing that piece with a new one). /forums/images/graemlins/tongue.gif
Good luck, John