Max effort cam for low comp 318

So I've been looking into gear ratio changes, nothing is going to be easy or cheap because the ratios I would want were never offered in a diff that is a direct fit for my car unless a rare 3.38 M3 diff falls out of a tree. That said, the following ring and pinion sets could be swapped into my current diff:

3.91 = 186 kmh @ 6000 4344
3.73 = 195 kmh @ 6000 4144
3.64 = 200 kmh @ 6000 4044
3.46 = 211 kmh @ 6000 3844
3.38 = 215 kmh @ 6000 3756
3.23 = 225 kmh @ 6000 3589
3.15 = 231 kmh @ 6000 3500

Just wanted to see how the numbers stack up with regard to top speed and the RPM shift from 3500 rpm with the current 3.15 ratio. The other track I might go to has a downhill run on the main straight, so it might actually top out given the assistance of gravity. If you watched the video above on the regular track, you would probably notice that after shifting into top on the main straight, it really hasn't got much left in it in terms of acceleration.

Shifting into top at say 5600 using the 0.7 split puts me at 3920, so somewhere between 3.46 and 3.64 seems like it might be the go with a tighter power band. That would probably leave me with only one second gear corner, more RPM thorough most corners and into top in 2 or 3 more places in the track.