Wait, let me get this straight: you have a cable coming from the FP with 2 connectors at the end, and you want to connect both of them; 1 to the MB and 1 to the card.
I don't think that's possible. I think I have a similar cable, but 1 connector is for AC'97 and the other is for HD audio. As far as I know you either use one or the other.
Forgot the search term I used last time, but they said you could lift a plastic finger and then the pin would come out, for what it's worth.
Could you give the brand and model of the motherboard and the souncard?