I've seen both heads from a V8 460 and I4 470. The 470 has an extra coolant port on the short side, which when blocked off, can allow a used 470 head to be used on a V8 460, but honestly, I've never looked at it the other way around. I will look tonight, likely has a press plug if the port is there. Plenty of aluminum heads out there, but its the exhaust port that is so heinous in flow on the 460 head that is the real performance limiter. Considering our stall speed of circa 5000 rpms, having the ability to make more HP at higher rpm's is not going to produce huge results. Some porting and valve help is out there for cast iron heads, but not sure if its worth the ROI. Still, I'm a bit curious to know the condition of the existing engine, compression, leak down. Given your speed results, sounds like it might be a little sick? At least it might be worth knowing if your going to part with it when your done with your conversion.