Including PSR's and TSR's , it may not be possible.
140kmph with 24 coaches - I don't think so. The loco is fit for 140kmph, but at a very reduced load. And there is a lot more here than just being 'fit' to run at a particular speed.
At any speed, the power output of the loco is used for 2 things -
1)...
more... Overcoming the friction and resistance of the coaches.
2) For accelerating the train.
The thing with locos like P4 and P7 at high speeds is that, they have enough power to overcome the friction, but very little left for acceleration (called acceleration reserve). So, they'll take a long time to go from 120-130 and and even longer to go from 130 to 140kmph. So, even if a loco is 'fit' for 140kmph, it can still struggle a lot to maintain a tight schedule as the acceleration available at that speed is very less.