I believe you are thinking too complicated. Just use header "B". Nevertheless I'm showing you pics of my 2009 MP.
![]()
In this pic you can see how I have replaced the black SATA cable "B" in the special harness with a red standard SATA cable. The harness remains in place though to provide header "A" with the SATA signal and both headers with power. On the logic board side I have capped the unused cable with a red plug to prevent potential short circuits.
![]()
Here you can see how I plugged into header "B" with a SATA power adapter to get Molex power. Header "A" is shown unplugged from the ODD.
Unless you want to fit multiple drives as i my case you do not need to go to all this effort. Any single SSD or SATA HDD will plug directly into your header "B".

In this pic you can see how I have replaced the black SATA cable "B" in the special harness with a red standard SATA cable. The harness remains in place though to provide header "A" with the SATA signal and both headers with power. On the logic board side I have capped the unused cable with a red plug to prevent potential short circuits.

Here you can see how I plugged into header "B" with a SATA power adapter to get Molex power. Header "A" is shown unplugged from the ODD.
Unless you want to fit multiple drives as i my case you do not need to go to all this effort. Any single SSD or SATA HDD will plug directly into your header "B".