360 stroker how much HP is picked up if everything else stays the same?

I think a lot of guys build stock stroke engines that are under performers. Talk to some of the guys that run stockers and listen to what they have to say. My sons stoke crank 360 ran 6.54 four different times at 3200 pounds which according to the charts is a 10.20-10.30 running a .620 lift roller cam. Same heads, intake, carb, and a .650 lift roller cam and a 4 inch stroke crank ran a best of 10.11