Check out this post from Yenko.net. The fellow restoring his Trans Am did a lot of research into plastic repair. Really Nice guy!! If you have any questions you think he might be able to hel you out with I would shoot him an email.

http://www.yenko.net/ubbthreads/show.../fpart/23/vc/1

http://plastex.home.att.net/

http://www.urethanesupply.com/index.html

Good luck!!