[DanEC]

I used a set of similar heads that KC ported/polished/installed larger valves - they were 1961 390 High Performance heads. My motor made 470 HP with a mild hydraulic cam and 9:1 compression. I asked his dyno operator what difference he thought aluminum heads would have made based on his experience. He said probably 30 to 35 HP. Of course I would have saved about 40 lbs or so, also. But, I wanted the heads for nostalgia. You may be less inclined towards that.