[CentOS] Replacing custom kernel with another - with same identifier

Hi list,

I just finished building a custom kernel from 2.6.18-53.1.21 source rpm
- this time with ISA bus and ISAPNP support which I accidentally left
out of my previous attempt. 
Unfortunately, this time I forgot to change my identifier in
kernel-2.6.spec file. Thus I now have one *installed* kernel version
*without* ISA support, and another one *with* ISA support but as rpm,
not yet installed. Both kernels now have identical identifiers.

What is the safe way to remove the previous installed kernel version
without taking out the uninstalled new version? Is the latter safe in
~/rpmbuild/RPMS if I use 'rpm -e' to remove the former version?

TIA

Antti