Hey Dan, it looks like they used 2 pumps (main and reserve) with a return and vent on the 2 small fittings. You'll probably want a blank plate over one and sender in the other. It should just be a matter of making an adapter plate between the hole and sender. I would recommend the inductive tube type senders from Centroid for it. Do you have a manual pump on the motor or an electric?
Rich the CCX tanks I've been making are 40" wide so are bigger capacity than this 36" I believe. Jeff has been under his car and sketched up a SC/Comp style tank for the CCX's that will have the look from underneath and some considerable capacity as it kicks out behind the rear wheels like this one
http://www.clubcobra.com/classifieds...t=1629&cat=500
If you're interested in the dimensions for that one let me or Jeff know I'm looking at building 2 like this already.