All I do, and there's absolutely no fiddling needed
I have several different kernels available and they all have the nvidia drivers ready to go. After installing, I recompile my kernel to something I like, then get the nvidia tarballs. I extract them and from the NVIDIA-kernel directory, I do "make clean" "make install". Then to the GLX directory and "make install". Edit my XF86Config, and that's it. Say I want to try 2.4.19, which I did, I download the kernel source, do make xconfig, then edit the extra version line of the Makefile. This step insures that the new kernel gets its own directory, and will not interfere at all with any existing kernels. make dep && make clean && make bzImage && make modules && make modules_install. Edit lilo.conf, run lilo, boot into new kernel. Once again for the NVIDIA-kernel, "make clean" "make install", then "make install" for the GLX. XF86Config is already set, so you can just switch kernels via LILO and both are configured with working Nvidia drivers. There was no tweaking, fiddling involved at all.
Too tired....no sig.