What's also fascinating to note is JD had a touch of Igloy in his training methods. Not that you don't see 20x440 in dad's senior year of training, but you'll see a lot of workouts with 110s, 120s, 180s, 50s, etc. Not a whole lot long reps. I've seen one workout that has 2x660 in it. In fact, as I am flipping through dad's 65 journal, JD had him start a lot of his spring 1965 workouts (from March on) with one 880 in 1:53-1:58, then run the rest of the workout. I mean, there are even days where it looks like a recovery day (or should be) and dad warms-up, runs a 1:53 880 then goes for a 9 mile run.
In a workout from early April 1965: Warm-up, 16x110, jog 880, 16x50, jog 880, 4x440 (62s), jog 880, 16x50 jog 880, 16x110, 2 mile warmdown.
A week later: Warm-up, 880 in 1:53, jog 880, 10x110, 10x50, lifted 15 minutes of circuits, then 8x220 on 1 1/2 min interval (30s), 6x330 on 3 minute interval (45s), 6x440 on 3 minute interval (62s), jogged 880, 6x110.