[CentOS] (OT) i586 kernel

What incantations are used to build vmlzi586 and initi586.img found in 
the isolinux directory of the CentOS 4.3 DVD?  I have an old K6-2 box 
that runs CentOS 4.3 fine but because of a few features, I'd really 
prefer to run FC5 on that machine and it won't install -- which is the 
reason for the (OT) in the subject.
I found this blurb in the specs file:
----------------
%define KVERREL %{PACKAGE_VERSION}-%{PACKAGE_RELEASE}

# groups of related archs
# Added i586 kernel support (CentOS-4)
#%define all_x86 i686
%define all_x86 i586 i686

# Override generic defaults with per-arch defaults
------------------
but somehow, that seems like too much magic in a too-small package.  
There must be a lot more to it!