Like said, a stock T Maxx will do approx 42/43mph out of the box when tuned well.
To hit 50 mph takes a good engine and some gearing changes.
To get above 60 takes a lot of time, modification and money. I have hit 63mph with a highly modified T Maxx quite a few times (big engine and a 3 speed transmission etc).
I’m trying to break 70 mph with my current S Maxx build. You have to forget about the time and $$ involved before even beginning to think about the 70 mph mark or you will be disappointed in the end.