Just finished installing Ebay seat heating kit in 2016 Hilux SR5 dual cab three weeks ago. This has the leather interior. Was a bit nervous about removing the seat coverings. Damn hog clips. But took lots of phone pics as I went. Put it back together using zip ties where the hog clips were a pain to reinstall. Wear gloves. Lots of sharp bits in there. Disconnect battery before removing seats or mucking about with seat airbag plugs. Be supercareful manhandling the seats out if the cab. sharp base conponents make it easy to scratch trim.
Fitted switches left and right just below shift assembly.
They work really well. Only need them for 15 minutes or so in the morning or when getting a bit stiff on a long drive. All up cost was about $70 including fuse jack from Jaycar. Did take me a full weekend to do two seats though!
Seen auto trimmers quoting $450 a seat for this.