i do that type of work nearly every day. i'd suggest looking at jcwhitney for misc. mandrel bends and tubing. summit and jegs also sell the same stuff, you may check their pricing as well. do not buy aluminized tube if you want your welds to look nice. for a first timer i'd suggest using plain ol' mild steel (cheap) and having it painted or powdercoated. if you're really happy with the finished product than consider jet hot. to start you may want to mock up the centerline of the system with some sort of hard wire (similar to a coat hanger). you should use this template to determine the bend angles you'll require, thus reducing the amount of scrap you generate. warm up your cut off wheel or chop saw and take your time, you may be suprised at how easy it really is. aaron