The base allows your body to handle and adapt to the harder training that is done during your pre-season and competitive season.
If you peaked at 35 mpw during cross, then build to 40-45 mpw building up for track. Aim to get there a couple of times before the start of track season. Each time you get to the mileage peak, you should be going a little bit faster. What I mean is this:
During cross you were doing 35 mpw probably mixed in with races and hard efforts. Therefore, building to 40-45 mpw should be easy. You should be able to get to that level in a couple of weeks after an appropriate break. Hold there for 3 weeks and let your body adapt. One of your runs should be a "long run" where you get 20%-25% of your total weekly volume in one run (8-11 miles for you). Don't schedule any hard workouts during this time. Run strides a few times per week and if you feel good on runs, finish them fast.
After 3 weeks at 40-45 mpw, take an easier week, for you maybe 25-30 miles. Maybe during this easier week, you run a time trial to see where you are at.
Then build go back to 40-45, only this time add in some structured training. Once per week, add in a run where you do about 10% of your weekly mileage at steady state effort (M pace on Daniel's calculator or Tempo Pace on McMillan's calculator). Also, once per week, do something where you are getting to your mile race pace, for you maybe 10 x 200 with 200 easy jog recovery. Do a long warm up and cool down on this day. Keep doing the long run
After 3 weeks of this, take another easy week. This should take you to the end of January. I don't know when track starts in your state, but if you have more time, hit another 2-3 week cycle as you did previously. Maybe make your repetition day 8 x 300 with a 300 jog and maybe add a very hard last mile on your steady state runs. Otherwise, keep everything else controlled.