Since turning 50+ have attempted something like the above, although now getting a bit too old.
2:54, 2:58 marathon (50 and 59)
Sub 1:20 half a bunch of times (maybe 8-10), half is probably my best distance
split 59:50 10 mile in a half a few years ago (so unofficial)
Only 35:43 in 10K
17:01 5K road 17:08 on the track
5:00.8 for the mile (more or less solo, in fact one race the 20 somethings were drafting of me and refused to set the pace!).
2:29:20, 2:29:40 for 50K XC ski (and did it at 50 and 55)
60s now and trying to break 3 for marathon (gotta dream)
Per the OP it's a matter of putting it all together, volume, getting in the right workouts at the right time, and paying special attention to the little stuff (drills-stretching, etc.), diet, and recovery/sleep. We have seen guys 50+ and 60+ runners just kill it (Dan King, Pete Magill, Brian Pilcher, Gene Dykes, Jacob Nur).