On the fact that he's staring with an 865 and the original query was an either/or question "would you do the 904 Big Bore or the Cams with headwork?" More horsepower to made with both conversions in tandem to be sure. I still doubt the claims of 10.5:1 compression in regards to a 904 upgrade to an 865. In his case a 90mm bore to 92mm bore and same 68mm stroke just doesn't increase the compression answer from 9.2:1 to 10.5:1 On the other hand, it does work when upping a 790 to 904...therefore more gain per dollar invested in flowing air/fuel through the motor by porting and hotter cams.
