Car dashbord communication with MCP 2515

But my question about the crystals is:
in post #6 I published a photo with all the crystals of the 3 devices.
they are not all the same value. Why not choose the crystal from dashboard (5MHZ) as the default value instead the crystal of MCP (8MHZ) ??

about measuring the CAN bitrate:


in fact i have a network with 50kbps because the value of a unit is 20µs.

So what should be changed in the code besides CAN 500kbps - 50kbps ??
The baudrate changes to??

thanks in advance