Paintable undercoating / truck bed coating / paint?????

[ruts87stang]

Since I have the rear end out of my GT I’m cleaning everything before I put all the new stuff back in.
The question is should I use a paintable undercoat, a truck bed coating or just simply paint it?

Thanks!

[stangster50]

http://img97.imageshack.us/img97/4140/43215d1141913572tlolnow.jpg (http://img97.imageshack.us/i/43215d1141913572tlolnow.jpg/)
http://www.stangnet.com/mustang-forums/621198-lol-now-rustproofing.html