have you read through Minuit's radio guide yet? There are good versions and not-so-good versions out there. It'll be one of the first threads in the DIY forum.
nothing in the middle, just lights in the b-pillars. there are a couple writeups on using newer LED housings in the factory location in the link in my signature.
are they interchangeable? I can't promise I can get back there, but the XJ just now showed up so there's a chance I can get back and grab the headrest off the other seat.