Thanks Red, I'm in the UK so some part names might be different, is the rocker panel the sill below the door?
I can see the grey vacuum pipe from the engine going through the bulkhead and a yellow pipe under the glovebox (left hand side under the dashboard) so, my guess is that the box I'm looking for might be behind the heater. I'm hoping that I don't have to remove the heater because that looks like a huge job.