I'll throw in my two cents. I'd go with a 500CI stroker kit in a 440. Some aftermarket aluminum heads, good intake and carb. I am not an expert at recommending cams, so I will delegate that to someone else. I would think nothing too radical would be needed in the cam area to get to 650 hp. But, if you are going to stroke any block (RB or Gen II hemi), might as well get the most cubes as possible.