Murphy will replace fellow Kiwi Craig Baird, who was initially slated to debut the car alongside Crompton, for the November 8-10 event.
Coulthard has in turn be moved across to partner Tony Quinn's in the category and circuit owner's Aston Martin.
Murphy, who endured a disastrous Pirtek Enduro Cup campaign with the Holden Racing Team, says he's excited to get behind the wheel of the McLaren.
McLaren is sending an engineer, Andy Scott, from the United Kingdom to configure the car to the latest GT3 configuration and provide technical support for the team throughout the weekend.
“Obviously the McLaren is a beautiful piece of equipment and I watched Bairdo set the Highlands lap record in it in March,” said Murphy.
“Both Neil and I are excited to drive the McLaren – with all the wonderful links of the McLaren name for New Zealand motor racing fans – in its Australasian GT debut.
“There certainly aren't many other cars like it.”
Murphy has already made two GT appearances so far this year, driving Jim Manolios' Trofeo Motorsport Corvette Z06.R at Bathurst and Queensland Raceway.
Having joined Murphy and Manolios at Bathurst, former Formula 1 driver Ivan Capelli will again pair with the car owner at Highlands Park.