My need for speed

Completed 6X400 at less than 2:15 each. This is part of my quest to complete a 27 minute 5k this year and perhaps complete the marathon in less than 5:30. Marathon training has not begun yet. The trick will be to maintain a balance between distance and speed. I have found that it is very difficult to maintain speed when building distance long runs. This has probably kept me injury free during the last 5 years of running. I will try to do both while being mindful of my body.