Lots of good sets here (though I think Doug's is much more for middle-distance and long-distance).
My suggestion: broken 200s on 4:00 with 8-6-4 seconds rest at the 50s, hold all 50s at or very near race pace.
Race pace would be the pace of your 2nd through 4th 50s on your goal swim. So if you want to go 1:50 split as 26-28-28-28, then 28 is your race pace.
Lots of good sets here (though I think Doug's is much more for middle-distance and long-distance).
My suggestion: broken 200s on 4:00 with 8-6-4 seconds rest at the 50s, hold all 50s at or very near race pace.
Race pace would be the pace of your 2nd through 4th 50s on your goal swim. So if you want to go 1:50 split as 26-28-28-28, then 28 is your race pace.