All you need to do/should do is to change the
in your /usr/src/linux/Makefile to something
personalised, and call the resulting kernel something
other than vmlinuz, and you'll be all sweet, able to
switch back and forth between old and new kernel
from your boot-loader (if you configure it that way,
that is ;}) ...
I do currently have 4 different kernels to chose
from in my lilo-menu (not that I use the other 3,
they are mainly experimental things).