The 68060 is the last in the 68K line. It can support up to 60Mhz, however the EC version will go as high as 80Mhz, but that version lacks the MMU. My guess is the lack of the MMU frees up some transistor space so it doesn't get as hot or something.
In either case, the 68060 @ 80Mhz is the fastest the 68k line goes to without being overclocked, and I believe its 120 MIPS at that speed, or around there.
The product is VERY expensive for its performance. The only reason to use it is if you want a fast CPU and you have some old code that can't be recompiled (assembler stuff) but you want it running fast. I would guess thats why NASA uses it - they probably have custom assembler stuff and its cheaper to buy a 68060 than to pay someone to port the code and reconfigure hardware for a new architecture.
