If I wanted to know if I was prepared to run a certain time at a specific distance such as the 800m or 1500m , what interval should I do?
To my knowledge, a 12x200m workout with about about 40 seconds of rest will give a close estimate of a time an 800m time.
Personally I want to know if I would be able to run a sub 4:25 mile or a sub 9:10 2 mile, but I want workouts to say I would be ready for it.
*This is without taking mileage into account.
If you want to break 9:10, and be able to do it consistently, I think the meat of your interval workouts should be something like 1200s in 3:30. 5 of 'em. These workouts should comprise most of your interval work in my opinion, and they should be run at a very manageable effort. You should feel a sense of cruising. On the last 2 reps, blast your last 200 in :30 or so.
12-14x400 at goal mile pace with 1m recovery will allow you to hit that goal pace in the race