Ed,
If you have any more trouble, give me a call. The metal plate simply bolts inside the door using the same 2 Alan head bolts that hold the striker to the for jamb area. This allows them to be retro fit without having glass in a plate with studs on a finished car.
The chain simply hooks up to the striker in the same place the pull cable is currently hooked up.
The original car used 2 intertwined springs hooked up the same way as we hook up a chain, I just found the springs didn't work well with the stiffer modern latches like they did on the original 550.