In high school I was a 46.7 400 (1:55 800) runner. We used to do 12x400 in lane 8 on the track. So our recovery would be from the finish to the lane 8 stagger. We did all of them under 55. I think the main point of these runs for a 5k guy would be to be consistiant and run them all around your 5k goal pace. If your all over the place then your not doing yourself any good.
Another good workout that I did in college was
3x400 30 secs between each
3x1 mile 45 secs
3x400 30 sec
so you do the first 3 all out to build up your latic threshold and then work the miles at your goal 5k pace and then work the last to as hard as you can. This workout really worked well with me. I have used it over the past year in my own workouts for a 5k and ran a 15:40.