A lot of what you pay for with the name brand I/Cs is the cast end tanks, which are very nice and have nice smooth laminar flow but cost a lot. Sheet fabricated end tanks are a good way to save money. Do yourself a favor and stay away from the 30" long, 6" tall intercoolers with the tanks on the left/right ends. I know they're popular, but they suck. They are crap for pressure drop and flow because of their length vs. cross sectional area. Go for a shorter, slightly more square setup. There is a reason why you don't see certain dimensional combinations from good intercooler companies; there are definate rules of thumb for intercooler design..

You can use crush bent tubing, just make sure that you go up a size to compensate for the restriction..