Probably the remote keyless entry box. I wish I had one of those... Other things in that area would be the memory lock module. I wish I had one of those too. Last thing in that area would be the speaker which mounts right behind the B pillar where the wiring goes up and to the back.
I am wondering if you made any headway on figuring out if you can retrofit a cluster with a tach? I found an 04 E150 in our local U pull it yard with one of those in it. I really want a tach... I haven't dug into that part yet.
On the CC note, I am adding it to my van. Here's what I know so far with a little background first. To begin, get the Ford wiring diagrams for your year. They are indispensable! I got both mechanical vols 1 and 2, the wiring diagrams, and the tranny book for like $60 on eBay. I thought, in my early research before I got a van, that Ford basically wired all the vans for all the options and then just plugged the boxes in for the options selected. That made sense to me. Easy to manufacture. Well, that's not the case.
I bought a 98 E350 bare bones no nuthin' for my platform. I was like, "I'll just hit the junk yards and pull the stuff I need." I did one better and scored a 2000 E350 Club Wagon XLT with a blown motor for $375! I got everything in one shot. I quickly realized that my main van did NOT have the necessary wiring. I have now had to buy a wiring book for the 2000 van (there were enough differences that my 98 didn't make 100% sense to what I was seeing in the 2000 wiring harness). I tore the 2000 apart and have both under dash harnesses ripped apart on my garage floor right now. There's a lot of wires for the pw, pl, pm, cc, 6 speaker system, and rear HVAC that my van didn't have. I'll get there.
I'm long winded, bear with me cause I am to the CC. I would recommend pulling an entire steering column with the CC buttons on the wheel and replacing the whole thing. No steering wheel puller, no messing with the airbag, no messing with the clock spring. All good things. Plus, in my case, I get a tilt column as well! Like I said, the 98 is a bare bones no nuthin'.
Curiously, in my van, I DO have the connectors wired, in place and stowed for the CC servo box and brake pressure switch. They are located under the radiator expansion tank. I need to see what pins the go through the firewall on to see if they are in the proper place.
Anyways, that's what I got for ya. I'll keep you posted when I get around to searching for retrofitting a newer cluster.