Seems to me there are two choices for this.
1. You can either wire up the harness with connectors for all 8 possible cards (in which case you will have to get the missing molex connectors),
2. You can build the harness with enough connectors for what you have, and either
A. Install the extra 6 inch wires in the last molex connector and tape the ends. These ends will go to the next card when you build it.
B Don't install the extra 6 inch wires, but be prepared to rebuild this last connector when you need to. I think you will need a new set of those little crimped end things.
I chose to do 2A.
I would have just done #1, but I didnt have easy access to the molex connectors needed for it.
Building the harness is fiddly, and doing it neatly is hard but possible. Still it would be easier if I had 3 hands for this step.
There is a thread on here that puts forth the idea of using punched on connectors and ribbon cable I think. I chose to just use the supplied pards, as I think it's not THAT horribly difficult.
cAPS