MTeach at Melb is extremely competitive. This paired with the fact there's limited CSP/HECS places overall and the fact they offer guaranteed entry pathway to their own students first makes it extremely challenging. You might have better luck if you apply for a full fee place (wouldn't recommend putting it above a CSP place preference though)
I had a WAM of 77 overall and still didn't get in. They also use the CASPer test along with other things to determine entry as well. I would aim to do the MTeach at Monash as you'd be given entry based on your undergrad.
If you are sold on Melb over Monash for the MTeach for whatever reason.... it might be worth doing your undergrad at Melb so you have that guaranteed entry. To be fairly honest with you it doesn't matter where you go and do it, as long as you walk out of it job-ready (this is usually achieved through the placement rounds anyway so really nothing to do with the university itself).
When you go for positions, education is a career area that focuses more on experience and skills rather than the prestige of a university or course. Schools want to identify that you're the best person for the job and unfortunately a piece of paper in a career that requires a voice and an ability to emotionally relate, doesn't really do it on its own.