I don't know if anyone is interested in this, but here are photos of the Tekonsha (male) connector and the Ram OEM (female) connector. The male plug is labeled for colors the way it came from Tekonsha. The female receptacle is labeled for colors as it is in the Ram Classic. If I could find the pin-out functions for the vehicle side, I'd be home free. But I haven't been able to find that information anywhere, including on the MoPar site.
It seems to me that Tekonsha has the wire gauges mixed up, in that:
they have their Black 12 gauge wire (+ 12V power) connecting to 16 gauge wire (Red) on the OEM side, and
their White 16 gauge wire (12V - GND) connecting to the OEM Black 12 gauge wire.
The 2nd one, trying a 16 AWG wire into what may be a 12 AWG ground wire (vehicle side) is maybe not so strange, but tying what appears to be what supplies 12V power from the battery into a 16 AWG wire on the vehicle side seems really strange to me. When I was trying to understand how to do this on a vehicle that had no connector, the instructions all said to run a 12 AWG wire directly from the battery to the controller. (Well, they do also highly suggest installing an in-line auto-reset breaker in that circuit, and I wonder if there is anything like that in the Ram's circuitry.)
(It is the Red wire in the Tekonsha cable that has the in-line diode, to protect the vehicle computer's brake circuit from being fried by a voltage back-surge from the controller. That is, the current is only allowed to flow from the vehicle to the controller.) [I hope that I have everything straight here in what I've described. I can easily get confused.]
I realize that they (Tekonsha, etc.) came up with their own color codes, and there might be some miss-match with one vehicle manufacturer or another, or even all of them. But gauge miss-matches are not logical at all. No one in their right mind would do that, certainly not the vehicle manufacturer.
If you flip the adapter harness connector over to plug it into the vehicle connector, the Blue wire is the only one that matches color. But most importantly, it is the only one that matches wire gauge. Some people say that you have to reverse two wires on the Tekonsha harness to align properly w/ the Ram pin-outs. But it appears to me that three may need to be changed. Or maybe just the Black and the White.
Am I getting ridiculous here? (I suspect that my wife thinks so.) I just don't want to toast the Ram computer, and I don't really trust an auto shop to not just say "Put the terminals back the way they were, and plug it in and see what happens."
EDIT: CORRECTION OF AN ERROR I MADE - The Red wire on the Ram module is NOT 16 gauge as I had thought, and as I noted on the photo below. I didn't pull the wrapping back far enough to even see if it was labeled according to AWG at all - I just assumed that the vehicle would have only two 12 AWG wires, because that's how the Takonsha wire harness is. The RAM Red wire is the hot wire - hot even when everything is off. The 12 AGA Black wire is the GND. I still need to test the Green w/ white tracer wire to be sure that it will light up a test bulb when the vehicle is running and the brake pedal is depressed, but I'm pretty sure that's how it is, because the isn't any dispute about the Blue wire - it's always the one that goes back to the 7-pin trailer connector, for the electric brakes.
EDIT 02: On the last thing in my previous edit, connecting those two terminals, even with the vehicle running and depressing the brake, does NOT light up the test light. Perhaps it needs a signal from the controller? (If not, then something is burned out on the PU. It DID, by the way, previously have a brake controller installed - by the previous owner.)
My memory is getting a bit fuzzy, but if I recall correctly, the bell housing is different in the area where the clutch equalizer torque tube mounts. So save all you can from the old engine, if it still has one in it.
If it is not in tatters, and if you are thinking of making your own, or having a local shop make one, I would remove it as carefully as possible, to use as a pattern.
I replaced the headliner in another car myself once, and when I took mine out of the P15 I kept it in one piece for quite a while, intending to make alignment markings for each panel, but later forgot and took out the seams w/o doing that. My experience with the first one was that it is difficult to properly align the separate panels, and then you can have wrinkles, or some panels which will not reach in spots. The material in the other car was less forgiving, so maybe that would not be as serious of a problem here.