The frame rails are nothing special except folded metal. You could make a pattern from heavy card stock and have them created locally and save a lot of money. Those would fit your car exactly. That will save you the tarrifs and the shipping. 1,5 mm thick rails should be more than enough. The other option is to split structural square tube and if you can't find a sheet metal shop. That will probably be more expensive, but is an option. The fender brace is a very simple item you could save money having made locally too. I helped a friend with a street car project and rather than weld items to the unibody and increase the potential for rust we opted to use some of the structural adhesives that new cars get built with. It's been on the car for 15 years and seems to be holding up well.
Hope this helps,
Cary