In most ILs you can use any vehicle (car, bike, heli etc) by having your character in it before starting the mission replay. Go to the area the mission will start, in the vehicle you want, taxi another character there and start the replay as them. The vehicle will be placed wherever you were, or you will spawn in it (note that it may despawn in some locations).

Example below. You need to include this part in the video for submissions.