The 2.4L would be a 4G64. AFAICT the G63B code just indicates a 4G63 equipped with jet valves in the head (likewise G54B vs. 4G54), whereas the 6-bolt vs. 7-bolt 4G63s have more significant differences. There's been plenty of discussion about those here before, reckon "DSM" would be a good search term to dig those up.