I wish you the best of luck and I look forward to hearing how it goes.
My question about the splits was prompted by my belief that we can't really make claims about our bodies naturally settling into a particular pace if we're checking our splits every mile. If you run six miles without looking at your watch and the last three are at MP, fair enough. But if you're checking your watch you're aware of the pace even if you don't believe you're consciously speeding up.
That said, I do hope for the best for. I understand time's winged chariot. I'm 53 and the opportunities to set PRs are long since gone. I can only work towards age group PRs so I hope you can get your sub 3.