The base vehicle was still in pretty good shape. However, there was already some rust, and some parts were noticeably worn.
The EV conversion means quite some cost and effort, and so the converted car should not die prematurely or make annoying trouble due to rust issues or mechanical failure.
Since for the conversion I anyhow had to disassemble most of the car, I utilized the occasion for treating the rust and for doing some repair work, replacing most of the expendable parts.
The subchapter rust prevention deals with this topic rather generically, while the contents of the other subchapters are specific to this particular project.