OK, finally figured it out after following the code line by line. It was in the mcp_can_dfs.h file and wasn’t readily apparent because of the way it was worded\coded.
//#define SPICS 10 ///////////////////////Standard Arduino
#define SPICS 53 ////////////////////////Arduino Mega
#define MCP2515_SELECT() digitalWrite(SPICS, LOW)
#define MCP2515_UNSELECT() digitalWrite(SPICS, HIGH)
As you can see above, the SPICS is worded funny, i would have made the variable SPI_CS to make it clear. A little underscore goes a long way. As you can see in the code, i changed the CS pin to 53 here.