I looked into body kits for my 79 280zx with the thought that I could remove my damaged valence and replace it with the body kit. The price quoted (sorry, no details on brand name or anything) was around $650, which I believe included a fin as well as front valence.
In my case, the bodykit fitted on top of the stock valence, so wasn't really any good to me.
(This was thru NT Spoilers, Darwin)