Questions about 16v tranny in a MKIII

OKay i already have a tranny from an '89 16v Jetta GLI in my 96 2.0-- love it-- Here's my question--when it was installed my mechanic sais the switch or the plug for the switch--whatever--for the back up lights was different between the two transmissions- or a different place something like that-- how do i fix this? any kind of adapter, or a way to splice wires or something? help me out people. i know a couple of you out there have 16v trannys...
anyway, thanks for any help
patrick