I think it's the 105mm Bore that upped c/r. The +5 crank and 105mm Bore will only get better with more air flow. I will tell you this a +5 crank and 105 Bore =770 most make 68-79hp and 55-65tq and it's a great Ride.
It's hard to account for a single part in these equations. The +5 will provide significant power increases (TQ and HP) but the overall increase is going to be determined by the sum of all the components.
1. I.E. Cam selection with higher compression will be an important factor.
2. a customizable ignition curve
3. Big bore exhaust vs standard
there are more than a few 770's out there pushing mid-upper 80's or better. And widdle 727 strokers pushing high 70's