Not sure about the man maths, but the reduce rotating mass route has worked for me. If you're going to reduce rotating mass, you're best off reducing it everywhere you can so you can feel the cumulative effect, rather than just doing pulleys etc which you 're probably not going to notice much.
On my car I've got the pulley kit, flywheel, carbon prop and lighter wheels (although oem wheels already light). They're probably all worth a few wheel hp each. The prop is reckoned to be about 5 whp, not a lot but as I say combined with the others, makes a difference. More throttle response, better pickup. If you shorten the final drive as well, then you've got so much more push out of the turns. The standard ratios are too wide for an NA. I remember a Toyota engineer saying the ratios had been tuned for 'environmental performance'!!
Doing TSS last year, some of the speeds I was pulling on the straights weren't far behind the forced induction crowd. There's more you can do of course, filter, intake, header, exhaust, power blocks. It's possible to make an NA go quickly but to do it properly might cost you as much as forced induction!
Haversack