McLaren Engines was (is?) a seperate company from McLaren Cars. I don't know, but at one time it may have been part of the same company, but by the time of the GNX they were different companies.
McLaren Engines was part of McLaren Automotive Group, headquartered in the Detroit area. Again, McLaren Automotive Group was a seperate company from the McLaren Cars.
Some may recall the ASC/McLaren Mercuri Capri of the mid-80s.