"Net" meant "with all the accessories" -- stuff like water pumps, alternators, fans, etc. that cause drag and that that weren't required under the older "gross" rules. Even so, however, there were no hard-&-fast proscriptions about the actual testing regimen, which meant fudging the numbers was the norm. A few years ago (someone will chime in with when), the SAE published very specific guidelines for measuring engine output and most manufacturers complied, providing the first "accurate" power numbers for new cars and also providing, for the first time, a meaningful comparison between different cars, whether from the same or different manufacturers.
FWIW...