If you have the time, what I would do is advance the cam timing 4 degrees and just see what happens. I built a road runner for a guy with just about the same combination, and it went 6.90 on a good cool day. I had a Howards cam approximately same lift and duration with a 108 center installed at 106. The heads you mentioned might get you the tenth you need. I have seen converters pick them up a lot as well. You did not mention your MPH for the 7.15ET. What I usually look at is is the MPH high for the et? If it is then usually some tuning and adjusting is in order. If the MPH is right for the et, then usually you have to do something to make more HP to see improvements. Wallace calculators are free