Im in the same boat as you, I need to extend my harness but there is not as much information out there as I thought there would be. I have come to the conclusion that each year and model supra is different, so you will ned the wiring diagram for your model 7m, along with 1JZ, which you can find at Rick's 1992 1JZ site. You then need to convert from. When you have both diagrams you can either take the plugs from the female 7m harness and put them on the 1JZ harness, or you can take the male body plugs from the 1JZ and put them in your 7m. I think I am going to do it by switching the harness plugs, rather than pull my dash completly apart. Here's a diagram of what it should look like if you have a pre 88 Supra
Thats how you would do the body plug swap, the harness swap is the reverse. You really need a diagram so you get all the wires in the right spot. Im no expert at this, this is just the information I have gathered. I plan on printing off a harness diagram for my 86.5 NA Supra from my dads shop, and using the JZ harness wiring diagram from Ricks site to do my harness extension.
