Let me start by saying most Kernels are built for specific ROMs... or at minimum you should read enough about an Kernel to see if it will work with your specific ROM. I've had very good luck just using the Kernel that comes with most ROMs.
To check what radio you have loaded is simple... Settings > About Phone > look for "Baseband version", it might be under a Software version. Currently I'm running a version of the Official MR2 1.39.00.0627r.