Tempo training - This is when you run shorter interval workouts at the same pace that your race would be.
For example, I was a decathlete in college and our 1500m training workouts would be running 600, 500, 400, 600, 500, 400, with all runs at a 400m pace of 70sec (4:40 mile pace), and 2-3 min rest. Each week we’d lower that 400m pace and lower the rest interval a bit. After about two month-long training cycles, we were hitting at least 60sec 400m pace on all our intervals (A little faster on the two 400m runs). My 1500 time was usually somewhere in the 4:30’s, so those were about 70 sec 400’s. Keep in mind that was the last event at the end of day two of a decathlon, so if I ran one fresh, my pace probably could have been closer to our training runs of 400’s down in the 60’s.
Of course we had a lot of other things to focus on training-wise, so our other running days were 200m-based sprint training, and a few days of short stuff (30-60m). We also had two morning runs a week of about 2-2.5 miles. We usually ran those as fartleks (1min hard, 2min jog).
I would say if you’re not going to be running under 400, you probably have decent foot speed from your 55-200m training. You should definitely focus on the longer runs and 400m pace tempo training. If you’re running more than the mile, you’ll need more longer endurance runs, possible some 800m interval training. Your foot speed will be fine; it will be a while probably before your endurance isn’t the limiting factor on your times.
I didn’t notice if you said what level you were competing at, but your coach should definitely have an idea of what kinds of training program you should be running.
As far as weighttraining, you will lose muscle mass if your training a lot of long distance. Your weightraining should still focus on full body stuff though, like Olympic lifts, squats, and could still include plyos. You should definitely still work on core strengthening and hip musculature strengthening drills (like hurdle mobility drills, steps-over and unders, etc.) Core and hip stability and endurance are even more important in distance running because every step will be more efficient with a stronger core.