gp3video.exe is the program generates - from the gp3.exe - the new executable gp3v.exe (which is that one with the long replay).
But you have to run gp3video.exe by dos machine, like dosbox, and it creates the gp3v.exe in the folder of gp3.
then use gpxpatch to select the executable as gp3v.exe - and it runs the game with long replay - :
keys:
P, R starts the replay .
' go at the end of replay
; go at the start replay ( start of the race, potentially).
[ and ] fast backward forward