From the Website:
We carry an exceptional line up of headers and exhaust systems for the Fiat 124 Spider, the 131/Brava, the X 1/9 and the Lancia Scorpion. Our 124 header is the most state-of-the-art unit available for the Spider at this time. We also carry a direct replacement for the stock exhaust system.
The do have some stuff for the Fiat 850 family too but you have to look for it. I have read good things about these guys. I wish they were closer.
1565 Howard Access Rd.
Upland, Ca, 91786