B&M lock-up controller 700r4 & cross member question

[i heart square bodys]

okay im having some slight issues here. im in the middle of swapping from a th350c to a 700r4 in my '86. the tranny is an 88 trans out of a truck. i have converted it from electric speedo to mechanical. i bought one of those B&M lock up controllers for it and the instructions are good to say the least. i am having issues with the 4 prong plug in the side. when i look down inside it on the tranny there are 3 connectors in the plug out of the 4 prongs, but inside the plug that came with the kit there are only two connectors(for prong A & D), there is a provision for another connector, whats the deal with this? do i just plug it in and hook up the 2 wires (supply and ground) ? or is there something i have to do with this third prong(prong B)?

now for the crossmember... do i have to drill new holes in the frame for this ? it is kind of looking that way to me but i thought id ask anyone with experience.
thanks to anyone that can help !

here are the instructions for the controller http://static.summitracing.com/globa.../bmm-70244.pdf