Well, a lot of it depends on whether you're a 400/800 guy or 800/1500 guy.
I ran the same 800 times off of 30 mpw, and 50 mpw two years later, but had a faster 400 than most of the guys I was racing in college (who were more 8/15 guys)
Some workouts that could indicate 50-51/1:55-56 might be:
2 x 800 special (run 400, jog 200, run 200) in 56/28
4x400 w/ 5 min rest in 55-56
8x200 w/ 2 min rest in 27-28
10x200 w/ 1 min rest avg under 30
500, 400, 300, 200, 100 at 56-57 per 400 pace. 1 min per 200m recovery
Like any event, spending time at race pace is pretty critical. Of course you could longer intervals at a slower pace to build strength early in the season. But there's no point in doing anything slower than mile pace. If you're doing stuff at 800 pace, do a mile of intervals; if you're doing stuff at mile pace, do 2 miles of intervals.
This is letsrun, so people may disagree with this, but this is a good rule of thumb for coming up with the rest for an interval set:
400 pace: full recovery
800 pace: running time x 4 for rest
mile pace: running time x 2 for rest
5k/10k: running time x 1/2 for rest
You can always do less rest than this, but if you're getting much more, the workout won't really indicate much except your ability to do pretty fast workouts with a lot of rest.
Good luck. BTW - if you're a sub 50 guy, you can go out in 55-56 and hold on. If you're a 52ish guy, even splitting is the way to go. You just have to really roll the last 300 to make that work.