Do you mean just angle steel, that wrap around the rocker panel?
You really don't want to go to Lowe's they are rediculously priced, and pre-rusted.
Hey, I just remembered - call Atlantic Scrap. I went there and got a "scrap" of 4x4 .250 5' long angle for only $10, that's what I made the XJ bumper out of. They had longer pieces but cut it to that length for me.