The 1JZ body harness is the same as the stock USDM that was used with the 7M for that same year. Well... it's routed different and the wires are different lengths, but all the same wires and plugs are there. You should be fine using a USDM wiring diagram for the 89-92' cars. If you already tried this and I'm wrong, sorry.
I don't know for sure, I'm just basing it on the fact that the JDM 1JZ engine harness (out of a supra) plugs right into an 89+ USDM body harness, so it should be wired the same.