In order to replace the 50 MHz 68060 with a 60 MHz one, all you need to do is replace the actual CPU itself, and replace the oscillator with a 60 MHz one.
But why not just overclock the 50 MHz 68060 chip that's already there? Mine's been running at 60 MHz with no problems for 3 years or so. Have a look at
http://members.iinet.net.au/~davem2/overclock/csppc.html-Paul
