I made it from 3.5" aluminum pipe using a mig welder at work. I got it powdercoated to seal up any possible leaks and give a cleaner look :)
Here's a couple pictures:
http://www.gotstang.com/photodisplay...1&showimage=49
http://www.gotstang.com/photodisplay...1&showimage=50
http://www.gotstang.com/photodisplay...1&showimage=57
http://www.gotstang.com/photodisplay...1&showimage=58