If your using the kb399 domed pistons that might limit your choice and as well keep in mind is what your going to gain going to be more then your going to loose with the heat dissipation with the al vs iron head.

Port volume on the al. heads are going to be min. 170cc and thats a good bit for a teener.

The pro comp at 64cc then take away your 6cc dome and your at 58cc.

When I factored all this into my lil 318 I just deceded to use my worked 2.02 J heads.