I highly recommend going into engineering if you want a good CRU at UdeM. With my 3.65/4.00 at McGill (Mechanical), they calculated me 37.706 of CRU! Which is insanely high considering that 3.65 is not that impressive.
The department of Bioengineering is the newest addition to the faculty of engineering at McGill (created in Fall 2016). I'm pretty sure that a GPA of over 3.5 will get you a very good CRU, since it's still a small department and they're very selective (the averages are also low since its engineering).
Aerospace at Concordia is also a good option. I can't really predict the CRU that you would get with a good GPA there, but since it's the most selective department (minimum R-Score of 28 right ?), I think it would be a viable option.
If you're going to apply to Med or other related programs, go with Bioengineering since you'll have some human physiology/anatomy/biology classes in your curriculum.