Mid 30s, how to determine my goal 800m time this weekend?

Yeah, in theory we are similar. I have convos with myself all the time that the best I can do is race somewhere between my eighth grade self (62/2:22/5:03) and 7th grade self (5:29). Even though I am stronger, I am also bigger.

Those are the breaks of getting old.

And the 5000 isnt so cut and dry. Yes, you may have run 16:55. But as a late teenager, at least in my case, it was more along the lines of aim small, miss small for 5000/5k. An unsatisfactory race in xc was maybe 10s off my best. Whereas now, an unsatisfactory race could mean the wheels fall off. Yes, I can run mid-to-low 17s but if something goes wrong I'll be in the high 18s or low 19s real quick.

It's different for sure.

As you get older, the aerobic work gets comparatively easier. The faster intervals become harder. Focus on those. You must get yourself used to fast, hard paces again.

Workouts like 500,300,4x200 cutting down the pace.

With similar hs times and similar mid 30s times I've run 2:07-2:08 a few times, never with any sort of race prep. My aerobic capacity is much larger now, but I don't think I can crack 57 in a 400.

I would say sub-2:10. You've always had decent speed. Should be able to run faster for 800 than what your 5k equates to.

You can definitely do better than mid-30s. That's over 1 hour mile pace. You can run at least twice that fast.

"when i was" is useless unless you are the same health, fitness as then and never stopped doing the same workouts. if you shut down you are starting from scratch.

the better way to go about this is first time you just give an honest effort and lay down a marker. then my process is chip seconds off. at longer distances i would say 5-10 seconds. at 800m i would chase a literal second or two in improvement. there is no sense in making yourself miserable setting down an initial race goal when you have no idea how you race now, and likely have over-estimated your speed where it will be depressing. dwell in reality, set a first time, then work from there.

another thing, my experience if you get caught up in what you used to do, this is no fun. you either need a clean slate or IMO run some distance you didn't use to do where you aren't competing with 18 or 20 year old you.