Forget the expensive shoe advice. All you need are your basic canvas sneaks and proper motivation. You'll hit that target heart rate in a jiffy.

I'm not nearly as capable as I was.Damn, you're fast. I run a 5.35 mile and 18 minute 5k. I wish I could get up there more but with my frame I'm not built for running that well. 5'11 218 lbs. I lift a lot so it's lots of weight to put on my knees. I also smoked for 10+ years and it's still effecting my breathing.
The next thing I would say is ASICS ASICS ASICS ASICS ASICS. Disregard anything you hear about anything else. Real Runners mainly wear Asics, unless there is a specific reason why they don't. Find a man that runs 20+ miles per week and he will likely have a pair of Asics on. Order them online to fit your foot. Use their easy to use system to do it. It's a great process and ordering new shoes every3 months (half year or more for you probably) keeps you into running. The system they use is recommended by lots of informed runners.
Interesting footnote to that bit of information: Pheidippides keeled over dead just after his proclamation and a pretentious runner's stare.