My K-Mart Diehard maintainer came with 2 short adapter cables. One cable has 2 alligator clips and the other cable has 2-eyehole connectors. Both of these short adapter cables can be plugged into the main charger unit using the 2-prong plug.
I cut the 2-eyehole cable adapter in half, stripped the cut end back about an inch. Next I took about a 5 ft length of black lamp wire, slid 3 lengths of shrink tube over the wire, one for each wire, and then a larger one to go over both wires simultaneously. I then soldered the copper colored lamp wire to the red side of the adapter cable and the silver colored lamp wire to the black side of the of the eyehole cable-half and then heated the shrink tubing to seal/insulate the solder joints. Note: it's important to know which colored wire is attached to the red positive side and which is attached to the ground side so you can match it at the other end of the lamp wire. Place the eyehole connector next to the battery where you plan to attach it, but don't connect it yet. I then routed the 5 ft of lamp wire across the front of the GT under the tub (battery cover) to the driver's side of the car so it can't be seen with the tub installed and secured it at a few places. I found a small gap between the fender and radiator frame that comes out right behind the tow attachment fitting. I then cut off any excess lamp wire and/or adapter wire, put heat shrink on the other half of the 2-prong adapter cable, soldered it to the lamp wire (matching the positive/negative wires), and used a black cable clamp to attach the 2-prong plug to the support brace. I found a convenient screw at the very top of the black brace which is next to the tow attachment point. Now attach the eyeholes to the positive and negative cable bolts on your battery. Once installed, you can't see the 2-prong plug unless you get on your hands and knees. As soon as I park the GT in the garage, I reach under the front and plug the maintainer into the 2-prong plug. I then drape the car cover over the GT. Works like a champ and no one has ever noticed it or mentioned it to me at any car show.
Hope this helps,