Can you update stock 2.1 rom with new kernel?

[Guest mistermentality]

I have a UK black GT540, rooted and running the standard updated rom from the LG site which I believe is 2.1 and I have the setcpu app as I would like to overclock the phone. I am a newb to it, and have searched the forums, but doesn't seem very easy to me so was wondering could I just update the kernel somehow and keep the rom I have but have the overclock benefits as currently setcpu does not allow me to go above 600mhz?

Any help appreciated, thanks :(

Dave