Here are a couple of websites you can check out.
http://www.difftechnics.com.au/gto/
http://www.tbyrnemotorsports.com/gtointro.html
Why are you looking for a one piece driveshaft? There are plenty of GTOs running 700+ rwhp with the stock one with absolutely no problems. Some are hitting the tracks alot with drag radials and still not having problems. I don't drag race mine too much but with 500 rwhp mine is holding up pretty well.
