There’s an old thread about Sprint Capital/Gatlin in GPP from someone who was in the camp. It seems to have started with 4X10+4X20+4X30+4X60 3X/week, alternating with ext tempo of 200, 300, or 400, 3X/week roughly 1500m/session.
Later in GPP, they moved up to 3X3X90. Charlie ought to know: He wrote the workouts for Tim, remember.