I have an 89 mkiii supra. The original engine was a 7mgte and I've read a few forums to do a lil homework. I have the 1jz w/ a 5spd and i know you have to extend the wiring on the ecu to reach the hole in the firewall being a lhd car. My question is that the connectors for the ecu and under the dash. Do you have to cut the connectors off of a 7m harness and wire them up to the 1jz harness or is it simply plug and play once you extend the harness?

yes you have to cut the harness and put the 7m plugs.