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I haven't swapped one in but I did install one from scratch on my 04 E350. I bought a Hoppy 7/4 pin combined connector and spliced it. I soldered the wires and covered the connections with heat shrink tubing to guarantee a good connection and protect from weather. I think I spent 30 minutes doing the actual splicing. If you can find a factory F150 connector you might be able to swap out the pins between the connector housings.
I used Hoppy model 47185 and cut off the four pin connector to hard wire everything. I think I got mine at Wal-mart but it could have been at Northern Tool instead.
Buy a second 7 to 4 way adapter, stuff it into a zip loc bag, and zip tie it up under the bumper. For $5 it's the easy solution I can think of. I keep one in the van and one in the trailer emergency box just in case.