This is a qoute from another post, this is all thanks to DemonSVT:
Most likely this pulley will underdrive the alt by 14-20% tops (500-700rpm at 3500)
Also in order to be pulling 140amps from the alternator you would need every electrical component working at the same time. Likely more! They oversize the alternator as to NOT ever task it at 100%. Also most alternators actually have an output over their rated amount.
I personally have sold a Worldwide alternator for a 98 Duratec that spec'd at 156amps at 4300rpm (rated at 135amps) I've seen some 120's tested as high as 160. Worldwide ships a test spec sheet (amps from 0-7000rpm) with every alternator they remanufacture.
The huge factor to think about is with the UDP at 6000 crank rpm the alternator is spinning at 4800-5200rpm (depending on %) and 7k @ 5600-5900rpm. That's a major factor in longevity to not overspeed the alternator. I searched for a UDP for the alt for this reason alone. Depending on the size of the one being made by this shop I may??? get another one if it's smaller. I think it's that big a deal. (plus if I do go this route I can resell the alt pulley I have to a Mustang buddy )
I smoked a couple alternators on my Conquest before I hunted down both a better alternator and a larger pulley. (7500+ rpm intercooled turbo) I knew the rev happy Duratec would not be easy on the alternator.
Take everything said here and magnify it 3 fold about the P/S pump. High rpms = frothed & burned fluid = possible failed pump/rack/etc. Not to mention you DO get a nice perfromance gain by slowing down this hydraulic pump! (I.E. parasitic drag machine) Mobil 1 ATF a major plus!
And there is plenty more here, If yu have not noticed I have been doing my homework on these, And I feel these are a great Idea.
http://www.contour.org/ubbthreads/showflat.php?Cat=&Board=perf&Number=75483&page=1&view=collapsed&sb=5&o=14&fpart=1&vc=1 -Jeff-
You can be Phil too if you'd like.