Canon 18-55mm III or IS II
The newest 18-55 III (non-IS) has the same optics as the 18-55 IS and 18-55 IS II.
Counter-intuitive though it is, I suspect you are right. The block diagrams are identical, and it's probably cheaper to make two lenses in which the only difference is a fixed element in place of the IS unit, rather than two different optical formulae.
For the very small price difference, I would still choose the IS version though - unless it is certain that the camera will only ever be used on a tripod.