3.5 and 3.9 require an 020. Some of the new modules in Devs:AmigaOS ROM Update only exist in 020 versions.
There was a project a while back called TwinKick, in which a few guys made (found?) 68000 versions of the modules and posted a video of an A1000 booting into 3.9. As I recall, Amiga Inc. hassled them about it.
