A friend turned me on to this site, which BTW looks great. I'll start by contributing these small tidbits about parts for S4 Spiders, which I discovered this weekend while working on my new S4:
A replacement air filter element can be found at NAPA, as part #6209, which will also work on the S3's.
The serpentine belt is NAPA part #050565 (11/16" x 57"), while the V-belt is #7325 (25/64" x 33 1/8"), both made by Gates.
The oil filter can be substituted to a Purolator Pure One #PL14670 and the fuel filter is Purolator #60146.
Hope that helps some of you guys who like to buy parts locally sometimes. I've been driving Alfa's for many years, but this is my first S4, and it seems like a very good example. Just a few more details to work on before it's 100% - the A/C is inoperative, and the foam in the seats is lumpy, due to a poor job installing the new leather.
Yeah, I'll have to take some pics. It's a silver car with tan/black interior. Many years ago I had a silver '72 and always liked silver spiders. Thankfully this one is all stock, unmolested, and was well-maintained. I've got all the receipts back to '92 when it was purchased new. The original top was recently replaced with an original Alfa/Pininfarina top (still the best, but pricey), and the seats have been reupholstered, but the seats weren't done all that well. They look great, but the back cushions are lumpy, so I'll have to pull the covers and see what the problem is. I've got a hardtop, too, but it's not matched to the car, and getting it repainted is on my list, too. A white top on a silver Spider just looks silly, but the hardtop is otherwise as new. FWIW, I've also got a red '74 Spica Spider in the garage, which I've had since '98.