I had a buddy weld mine up, I don't know how much he charges though. I basically did everything except for the actual welding. I got the axle, bought the steel, cut the miters, etc. He welds roll cages for 4X4s so odds are, the welds are strong. This is his website:
http://www.jkcustoms.com
I bought my steel from Westbrook Metals, behind Highland Mall. Their prices are a little on the high side but they will cut the steel for $5, as many cuts as youu need. It's pretty hard bringing home a 22ft piece of steel in your pickup.
http://www.metals4u.com/
I bought my axle in San Antonio from
http://swgooseneck.com because I thought they wouldn't charge me shipping since they are a dexter dealer. You can get Dexter Axles from Stone's Trailers over on I-35 near 1325 (or 45, or Louis Henna, or whatever it's called). I actually talked to them first, they will put in a custom order into Dexter, the price was the same as the place I bought mine from.
http://www.stonestrailers.com