Got a 140a universal alternator from
great bit of gear, so far can highly recommend one of these over your standard 120a bosch upgrade, for fitting all i had to do was make a new spacer, and drill the pivot hole out to suit my bolt, and make a serious charge cable.
from tests so far, it'll do 14.35 to 14.40v at idle with measurements taken from back of alt and in boot at battery, those figures are with BOTH 16" thermo fans running, along with the holley blue pump, and headlights on high.

the alt is advertised to do 90a at idle and full 140a by 1800rpm.

dont think i'll be having any battery flatness issues or cutting out due to low voltage at summernats 2011.