For the rear plugs like this kit? You don't. Not without pulling the trans. Get the Lethal Gen 2 mod. Its better anyway since it sends the coolant forward to the radiator return instead of bottlenecking 2 heads' worth of coolant at the heater core. And since it installs in the top freeze plugs its easy with the engine in the car.
While I tend to generally agree with this HCM being difficult and unservicable should something go wrong, with regard to any bottlenecking, as long as the restrictor is removed from the heater core supply hose, there is no potential bottleneck.