Hybrid cluster completed! Installed my original speedo, and oil pressure gauge into the tach cluster case. Used the original bezel and lens as well. Plugged it in, wired up the tach and it works! No re-pinning needed.
Also I used the SES light and "overspeed" lens from the C60.
I should mention I did not pin these lights into the cluster, rather I used GM marker lamp holders wired separately into the TPI ECM. The "Overspeed" light will be my shift light
. Sadly this leaves me without a "brake" warning lamp. Working on that one.