Question About Metco Lower Pulley Kit

[THunterW]

I know I should know the answer to this, but I've never installed any aftermarket lower pulleys on either my Lightning or Cobra, and the only time I've had the factory lowers off was for accessory and supercharger belt replacement on both vehicles. My question is, while looking at the Metco 4# lower pulley kit with the brackets, where does the hub that the 4# pulley attaches to, mount at? I see there are 3 holes in it, does it bolt into the factory harmonic balancer somewhere, or does the factory balance get replaced? It's been a while since I unscrewed the factory supercharger pulley from the reverse threaded hub, and don't recall seeing any 3 open bolt holes anywhere? The only time I've ever added any aftermarket pulleys was to a V6 F-150, and I added an ASP underdrive crank and overdrive alternator kit, and the underdrive crank pulley completely replaced the factory harmonic balance/pulley unit, so this is why I'm asking this question. Thanks guys.