http://www.cdc.gov/nchstp/od/gap/pmtct/Trainer%20Manual/Adobe/Module_6TM.pdf
Page 11
Number 4
3 months is considered that conclusive hiv antibody test window period.
That being said Dr Hook and Dr HHH had said on many posts that at 6 weeks 95% of new infections will show postive at that time.At 8 weeks over 99% of new infections will be postive.Im not quite sure where the 80% figure posted above comes from.Im am by no means an expert at all but i figure i could relay some info from 2 experts in this field.I hope this helps..
3months can give you a conclusive result
74days can only be right for 80%
good luck