I lost the link but it wasn't too hard to find on Google. But there was some place that had all sorts of fabbed metal sections like that. I was particulary interested in the 'half sill' replacement package - an outer skin, and the bottom half of both inner sill layers - replaces the normally rusted parts without resorting to major disassembly in the tricky front and rear and upper sections of the sill. But the site had lots of other parts too, like frame rails, fender patch sections, etc.

*googled it up*

http://www.alfaparts.net/p1800.html