Ex-Master runner here. You sir, are either very, very good, or toying with us. In the last 10 years only two Americans 60 or older have broken 5:00 for the mile. Tom Bernhard, 5:59 and the legendary Nolan Shaheed--4:53 at age 62. (At 60, he only managed 5 minutes and change.)
I'll assume you are very, very good. Here's my experience, then: I started running at 48. Low mileage--15-25 miles a week. Occasionally, some old HS interval workouts. Throughout my 50's I kept trying to meet the US Masters T&F All-American standards, but kept coming up short. e.g. 2:18/5:14 at age 51. At 60, I decided to pull out all the stops. I still kept the mileage low--prob about 20 a week, but got hold of Jack Daniels Running Formula book and used that as my guide. (I modified the workouts due to age, but I followed it fairly closely.) Living in Eugene, I had access to excellent PTs--who worked a lot with runners. More importantly, I had a great massage therapist--former head therapist for the NIKE track and field athletes. (Avoiding injuries is critical.) With Daniels plan, and great therapists I was able to meet the All-Amer standards in the 400, 800, and mile. (In my case, a measly 5:55 mile). And of course a lot of stretching and core work.
Haven't run since then, but wondering if I could meet the standard--sub-10--for the mile at the ripe age of 71.
Good luck to you!