Trying to help a friend with a 440 street build and I have a question about factory cylinder heads. Here is what he has. 440 block bored .030 over,stock stroke,with a set of KB237's pistons set at 0 deck height and using a FelPro 8519PT head gasket. He has a set of 516 closed chambered heads with a mild port job he would like to use, and wanted to use the mopar 509 cam. This is going in a 66 Belevedere with a 3000 stall converter, 3:91 gears and plans on mixing fuels.
Would he be better of using a different open chamber head milled down, like a 906 that would flow better than the 516's. He wanted the compression set at 11:1, but I didn't know if a open chamber head could be cut this much to get close to the compression he wants. Anyone running this bottom end combo with factory iron heads???

Thanks
Dan