I found this path finder tool:
I guess i was on the right track.
1. Should i upgrade both PSC's first to 6.7 U1 via "update" option in the vCSA Installer ISO.
2. Then Migrating both vCenter Servers to vCSA 6.7 U1 via Migration Utility ?
3. And then use the convergence tool in 6.7 U1 iso to migrate from external to embedded PSC ?
So this guideline should work.
But at Point 2 i still get this error message when using the Migration Utility to migrate Windows vCenter Server 6.0 to vCSA 6.7 U1:
"Cannot upgrade vCenter Server (Appliance) with an embedded Platform Services Controller, because Platform Services Controller is installed remotly on x.x.x.x."