I made a mistake in indicating the device. I was referring to mcp2122 that does not have a clock. Fortunately I have both chips, so I think using the mcp2120 solve my problems.

But the problem remains if I decided to use the mcp2122 which requires only an external clock with oscillator ottenible of 14.7456MHz.

From what I understand you can not change oscillator and hope that everything keeps working?