hmmmm,
You mean the fact that for every increase in BPM there is a linear increase in pace ?
Well to do that I'd do one of those Hadd tests on a track and run 2400 at 140, 150, 160 ,170, stick the results in excel and get the gradient and intercept. Or just take take two runs at different HRs and interpolate.
E.g. I think my gradient is about 3.8 secs/mile/bpm (most people seem to fall between 3 and 4, from my analysis of errr 5 people) as I run about 6:10 @ 170HR and ~7:35 @ 145HR
But I'm not sure how that helps predict race times though, unless you know the average % HR you could hold over the distance, e.g. 1/2M, but then that will depend on where your LT is, so you need to know that first.
Of course you could use the old 16 per mile for double the distance rule, but thats only a guideline for when you are aerobically "fit" and does vary quite a bit from person to person (so I've heard)
Think I've probably confused you... :-(