I'm more of an endurance guy, so I know the marathon will be my best event. My 5k pr is 16:53, and my track times are horrid at 2:20 800m and 4:48 1500m. I'm training for the 1500m now to improve my speed. Long term, I'd like to average a sub 6 minute mile pace for a marathon, so under 2:37:12.
What should I get my 1500m and 5k times down to before moving to the marathon so that I'd have enough speed to reach my goal?