This was a factory blunder. Yes, the early sticks were too short. The true recomended capacity w/ a fresh filter is 7.5 quarts. 8 will not hurt it. The oil cooler is factored in. It's hard to ignore the stick, but if it will make you feel better, completely drain,add new filter,add 7.5 qts. start it and let run a couple minutes, shut it down, let it settle, and remark the stick as full. All years have the same capacity. Looks like someone didn't know this and went by the stick before you bought it. Cams are up top, so you don't have to worry about the lifters going hydraulic, and I think I've read in a Northstar article that a windage tray was designed in due to the high RPM capability of the engine. So hopefully no damage was done.