You could tell from the dusty, yellowed and faded packaging that this was some oooooold stock, but I suppose that's to be expected. Just as indicated the wiring harness was entirely plug-and-play. Nice!
$45.05 - Trailer wiring harness (Hoppy 43755) from keenzo.com
*This harness is listed for late 80s/early 90s B series Mazda pickups, but other NA Miata users have used it and say that it is a direct plug-and-play solution.