Closest I've got is my 116 Giulietta which has basically SZ running gear. Primitive is how I would describe it. I recall last time I was horrified at how heavy the steering was, for example.
An SZ should be pretty much dead cheap to run. It is, to all intents and purposes, a 3l 75. There are some parts (headlights for example) which are, apparently, impossible to get. I think they can rust as well, but the mechanicals should be pretty simple.