VF, impressive mileage. You'll find the speedwork comes really fast; it was only a couple of months ago that ID was doing super-slow mileage, and then started doing his first few strides and hill sprints.
Out of curiosity, what's in your core routine? So many people mean so many things by that term...
Tuesday reminded me what a good speed session felt like, and today reminded me of what the day after feels like! Plodding a good minute per mile slower than usual. I think I've figured out a weekly pattern for the next month:
Tue: mixed hill session: drills/bounding, set of 1min reps uphill, 10min tempo or 2x1000m or some such afterwards
Thu: circuit; followed by 1-2 sets of heavy weights; then 6-8 short hill sprints after.
Sat: either (local 5k time trial + hills after), or repeat Tuesday session
Sat or Sun night: gym work, excluding glutes/quads/calves if tired
'mixed hill session' will involve some drills/bounding, a set of reps with jog back, and either 10min of tempo or a couple of flat repetitions. I discovered that Loughborough (our equivalent of Oregon) do these kinds of sessions regularly - always some flat running before or after a hill session.
Since the hills are pretty tiring on the legs, my previous habit of doing weights later that night or the next morning isn't going to work any more. I'll make Thursday the day for muscular stuff, and always have an easy day between the quality ones. For the second gym session at the weekend I will deliberately try to spare the main leg muscles, but will work the things running doesn't: hamstrings, hip flexors etc. plus upper body
Hopefully this will work but I think this means I have to do burpees tomorrow :-)