Replacing 302 heads with magnum heads

I personally don't think the swap would be worth the effort. You might see a little difference, but not much. If you were going to do a cam, intake, and heads, then maybe, but not with what you've got. I had a 302 headed 318 in my Duster before I built my stroker, and it was a good little motor. I just sold it to a guy at work, and the only reason I sold it is because I'm going to be moving soon and needed to downsize.