I just finished mine.
here you can clearly see the vain.
and what I did to help me not drill pass that. I used tape to mark my drill bit and measured from the side to get me how far I would need to go. About 1/2" is all that you need.
On the second location I drilled on the side of the box....but, instead of 1.25" . I marked and drilled 1" from the seam. If you look inside your box where you are going to drill....you will see that the casting gets a little thinner passing that 1.25" and beyond.
I am assuming this is the one that holds the balls. Whatever you do handle it very carefully. I picked it up from the input shaft and the bottom started to unscrew. I caught it in time not to spill its guts. here is a pic of the input shaft
Here is your sector shaft God I hope I have this right.
this is my finding and I hope that helps some.
Took me the whole day to remove box from truck to installing it back along with the hydro assist set-up...including parts run(mig wire),breakfast and lunch.
I have a huge cooler so no mods where made to the resivour....for now.