Cobra and underdrive Pulley Question

So this is my understanding for cobra owners as far as pulleys are concerned. We shouldn't change our alternator pulley because the lights already dim a bit stock, and water pulley is smaller then the GT one so that should be left alone, so this leaves me to belive the only pully worth underdriving is the crankshaft pulley?
 
even though the cobra pulleys are "underdriven" from the factory they are still nowhere near REAL aftermarket underdrive pulleys. Aftermarket ones weigh less. That is the main point. Less rotational mass=more power. Same principle for driveshafts. I put a set of MAC pulleys on my 94' cobra (all 3 of them). Replacing the alternator pulley was a bitch because the nut was in there pretty good. Anyway the only thing i get is the gauge cluster dims a little bit at idle when im waiting at traffic lights with my lights on. When you just touch the throttle for a little bit of gas, the lights come back on to full power. When i say the lights dim, i don't mean they go almost completely off; i mean its such a small difference people looking at your car wouldn't even notice it unless they were really reallly looking. Thats my experience anyway. I say if you're gonna do underdrive pulleys, do them all. Not worth the effort replacing just the crank pulley for an extra 4hp or so.