Re: 6cm Vs 7cm Gasket Comparison.
 

Couldn't you just use equal length headers and get a similar effect? I don't know too much about it, but from what I understand the equal length setup is supposed to keep the pulse to the turbo even, similar to the twin scroll design.

Re: 6cm Vs 7cm Gasket Comparison.
 

I believe the evo manifold fits on a DSM bolt pattern wise. Probably need a spacer between the mani and head though, as the turbo will face the opposite way.