How to specify archetecture for package in ks.cfg?

["Hearn, Stan J." <stan hearn nscorp com>]

In my package list for and X86_64 server I want to specify several
packages with i386 architectures.  But using the version number doesn't
work.  

How do I specify the architecture?  Or do I just need to do that in the
%post section using rpm command?

%packages
compat-libstdc++-33-3.2.3-61.i386
libaio-0.3.105-2.i386
expat-1.95.7-4.i386

Thanks,
Stan