Actually, depending on what's in the way (such as air pumps and the like), the Spitfire is an easy car when it comes to buying filters. The earlier ones, all the way back to the first 1963 models, could take a Motorcraft FL1-A, Fram PH8-A (or PH16 with the adaptor), AC PF-13 (which I've used for years in Spitfires and Heralds), and a bunch more. Same as many 1960s-1980s Volvos, many Saab 99 and earlier 900s, and a bunch of even more common stuff such as Dodges (not sure which ones). The later Spitfires, needing a narrower filter because of air pumps and the like, might be a bit more limited in selection...but then, you found the AC PF-34, and I recall that being a pretty common filter as well.