I'm not familiar with any New GTM OEM options out there.

I went down the path of picking up the donor kit from one of the guys on eBay (around $4k as I deleted some items that I will replace with higher quality items). The parts showed up packaged nicely and were actually in pretty good shape. I have then decided to clean some of the items up and add new parts. For example I am going to powder coat the control arms, replaced bushings and ball joints. I went with PFADT bushings and Moog ball joints, and all included with the powder coating I'm into the cleaning up for about $1600.

Hope that gives you a little idea of just one aspect of the donor parts.