The instruction set to handle the MMU is, from what I remember, more or less the same.
Unfortunately not so. 68030 and 68040 use different supervisor instructions to access registers, (some) different supervisor registers and the register bit mappings are different, as well as page descriptors.
68030 MMU indeed supports more pagesizes, and in general is more flexible. I guess the MMU design was simplefied for 68040 to gain speed and reduce complexity.
68040 and 68060 MMUs are almost identical, 68060 just adding some more restrictions on cacheability of mmu tables and renaming few cachemodes. MMU exception processing is different on 68060, too.
