Not sure about how deep you can drill that hole but just a small suggestion to help with room. Try putting your left front tire up on some blocking. That'll make the right side pivot down and might get you a bit more room to work.
I'm interested how you make out with it. I have a TE-A20 that has an alternator bolted into the generator bracket and it doesn't sit square with the crank pulley. I want to replace the brackets to true up the alternator. I just need to find out if there is an aftermarket bracket or if I need to build one.