OK
The first thing is that the figures you give are, I think for the 6v Speed 400 and not the 7.2v.
The 7.2v has 16400rpm at nominal voltage and a stall current of 21A but importantly has a current draw of 3.3A at a maximum efficiency of 72%. This low efficiency at a low ampage explains why Speed 400 motors get so hot if you put a real load on them when the efficiency dips well below the 72% and all the rest is heat.
A Speed 400 7.2v thus has a kv of around 2300 but this does not directly translate to a brushless motor. A brushed motor when placed under load has a much greater tendency to drop revs than a brushless motor. For equivalent performance we are thus looking for a brushless motor of around 2000-2200kv which will happily cope with loads of 5amps without getting overly warm. The bigger & heavier the motor the cooler it will be. I confess that I like larger motors than strictly necessary for the lack of heat issues. If weight were critical for performance I could go smaller.
Your suggested motor would do the job perfectly well as long as you chose the 2200kv option.
I also like this motor at 52gms (Speed 400 73gms) and 28mm diameter (same as Speed400) which will give you enormous headroom when asked to do what a Speed 400 did. I have used, & abused, this motor in model aircraft with very good results.
https://hobbyking.com/en_us/d2826-6-2200kv-outrunner-motor.htmlLink corrected 11:25 but appears to be out of stock in UK at the present time.