1997 Explorer 4 pin trailer wiring

[allmyEXes]

I have a small utility trailer that has been in the family for ~50 to 55 years and it has a "flat" 4 pin connector on it. I have used it on various vehicles that the turn signals and brake lights are the same filament in the 1157 bulb. On my old Mountaineer it had an aftermarket "tap in" harness for trailer lights and it worked well with any trailers that have been hooked to it.
Recently I hooked up the trailer to the white '97 Explorer. Well the trailer lights don't match what is going on with the truck. I took out the rear taillamp assy and someone has been working on the wiring in there. A flat four has been "tapped" into and there is some blue tap in connectors and black tape too. I assume that the PO's trailer has "custom" wiring too. I haven't checked to see if the Y/G/B and white ground are where they should be but even if I where to wire it that way I think that I wouldn't have brake light because the directional signals are yellow and the brake lights are separate red lights.
Is there a factory built in 4 to 6 (maybe 4 to 5?) wire converter box built in the left rear quarter panel? or am I going to need a small converter box to go from 4 to 6 wire? I don't have a harness to tap in to the factory harness across the back to tap in to behind the bumper.
Thanks in advance for any advice.
ADDED: I believe I found the answer. I hope that this will help others in the future.
5 to 4 converter box
For today while I'm waiting on this device I'm going to wire the red brake wire from the truck to the brown running light wire so that I have stop lights and turn signals for daytime use!

 

[drdoom]

Have you looked between the spare tire and the hitch? My '97 has a gray plug there, with a weather cap. I bought the conversion whip and it works great.

 

[donalds]

I have a plug under both taillights I used the driver side

This may help

Trailer connectors in North America - Wikipedia

en.m.wikipedia.org

 

[allmyEXes]

Have you looked between the spare tire and the hitch? My '97 has a gray plug there, with a weather cap. I bought the conversion whip and it works great.

On my old Mountaineer it was done that way.
On the white '97 there is quite a nest of extended wiring that I will have to pull down out of there to find the gray plug. If that works then I'll delete the PO's additions...

 

[allmyEXes]

I found the gray trailer 4 pin connector amongst the nest of added wiring. I also found that if you open the left taillamp (pop it out of the quarter panel) You will find another gray connector. It is complete on the old Mountaineer, however, Someone cut the downstream part of the connector has been cut off after being unplugged from the source. I'm really not sure what someone was doing in and under there. I'll have to go to a salvage yard and cut one off a junk truck. Keeping wiring intact on the MM. The more that I looked at it, it looks as if it is the disconnect to unplug if you are going to remove your back bumper. It feeds the trailer light feed and the license plate illumination lamps.
I will add a picture Monday of the empty plug and chopped off connector.