GM launches NX through a customized environment, using a custom launch program. In the past, I ran both the GM toolkit and company customized environment from the same install without any issues....I just used 2 different .bat files to launch NX, and those .bat files specified which environment/defaults to load.
As long as you set your environment variables to point the correct locations and use separate customer defaults, you should be able to run multiple environments from the same install. You just don't want to overwrite what GM or Chysler have set up - try putting that portion in 2 different directories and see how that works.
You certainly aren't going to ruin NX by attempting to load both on one workstation - you'll just have to test it out, I'd imagine.
Tim Flater
NX Designer