Build 64-bit kernel on 32-bit system

[john wendel]

After reading some of the 32bit vs 64bit thread(s), I thought I'd build 
a 64bit kernel on my 32bit F8 box. Got the latest kernel source and 
stable patch from kernel.org and tried running make menuconfig. Much to 
my surprise, there isn't a 32 vs 64 bit toggle in the kernel config. 
Google confused me, but did tell me I require a 64bit toolchain. This 
seems bogus, since the kernel is self contained. I think it should be 
enough just to set the proper gcc options.

Could someone who has done this before provide some help please?

Thanks,

John