How much horsepower

That's a big stick, with the aluminum and 10.5:1. I'd have built it with at least 11.5:1 (yes, pump gas). But, I'd make a guess of 500ish at around 6400, with 480tq around 5200. IMO, the rods are not enough (I'm a firm beleiver in anything but SIR), but I tend to overbuild. I also think the cam is too large, but if this not a street car, meaning no need for idle quality or low speed running, low stall convertor, or mild gearing, it should pull real strong for a 360.