by modding these motors you may be able to push out another 10hp maybe
A modestly tuned 850 motor, with the poster's suggested cam and proper stage 2 headwork, makes almost 20 more rwhp and 10+ lb/ft of torque than a stocker. Trust me, I've been present for the dyno runs. I've ridden it too, full bagger, faired, touring bike. Still incredibly streetable and pulls like a freight train.
For what its worth, my 836 makes 30+ more rwhp than a stocker, and will make more with some additional fine-tuning. Dyno sheet and details are on the Hi Po page in a sticky.