Kay, I don't know about Apollo boards, but it is as I understand possible to replace an 040 with 060 on many turboboards (dunno if it's as complicated as Laser makes out, but then his posts so far rarely make sense to me)
Anyway, to answer your question, there's no such thing as an 80MHz 68060, the only go up to 50MHz. Of course you can overclock, (with the usual warnings - make sure you have adequate cooling and expect lowered reliability) and I've read of people using 060s clocked anywhere up to ~100MHz (from what I've read it's usually the Atari folks who get silly fast speeds).
Of course you could pay the manufacturers Freescale to develop a faster 060. :-P
