brass tang gets screwed to the case. Only fits one way. The cam only goes on the stud one way. If ya get smart and try any other ways, something will break and the sensor wont work 
That's just fact. I actually put a little dab of 242 threadlocker on mine, simply because it had fallen out of its place some time over the last 39 years.
It really can only go in one way, and once you get in there and look at it, you'll see how it's supposed to go in. As someone suggested in a previous response, even in the worst case scenario, you can put it in, mock up the shifter, and simulate some shifting action just to make sure you've got it right before you torque the sprocket cover back on.
As an added bonus, I ended up replacing at least two of the bolts that hold that cover on. I believe some of those bolts are 55s, while others are 32s, and mine were torqued on there hard enough and had been torn up enough that I needed an impact screwdriver to get them off,
and needed to replace them with new ones.
For what it's worth, I put a little Loctite on those too.
