Be careful, the 66-69 K frame is diff than the early K frames. You see the K member is diff moving the engine forward 1 1/2-2" compared to the later 66 up K-frames.
If it were my car, I would clearance the are needed with a carbide Burr and epoxy, or Mig weld up hole. Im pretty sure stock-ish style oil pans will fit with a clearanced K-member in the lip area.
Look at Mancini Racing web site for pans and pics.
I run the SS style pan with the drag link through the pan. My engine was/is at stock location. I located a Milodon pan that worked like a charm.
If you have a truck pan, or 4x4 pan like the Milodon pan I would just use it.