That 3 mile tempo would say to me almost certainly.
Do me and you a favour and go out and run 2 * 1k at 6:00 per mile twice in the next 4 weeks. You don't need to any other session and I promise you you'll be fine.
Read the post before yours...moran.
Way to go OP!!
Lol! You're right. Saw that after I posted. I quickly posted again. I was too hasty. Apologies.
Totally doable. I am 66 y/o (and a no talent runner) and have hit 5:52-5:58 each year since 60. It is a goal again later in 2023, even though I am currently in a training block for a 1/2 marathon.
Your 12x400 show strength. Wow. Right there you are probably close. We are doing 10x1:35/6 indoors tonight with 200 jog and I am in probably 6:08 - 6:10 race shape (spiked and paced)
I would suggest the following:
-Work in some 8x200 with 100 (easy!) jog recovery. If you are hitting :35-37s you are golden. (Note, I can barely do an average of :41 for this workout, but everyone is different)
-A 1200m TT a few weeks out will help you dial in. If you are at 4:30 or faster, great!
-Don't be afraid to have someone help pace you in training and the race effort. A solo <6:00 is tough if you haven't done it before.
-A couple short strides at the end tempos won't hurt.
^^^^^^^^^^^^^ Please disregard above comment. I was in a rush and didn't see you have already met your early goal of sub 6:00.- You have chunks more of improvement!