[CentOS] Rebuilding a Centos 6.2 netinstall initrd with an updated driver?

Hi all,

It seems that with the release of the X99 motherboards, a lot of vendors
are shifting away from using Realtek ethernet on board NICs and using
Intel. Our main distro. on the floor is Centos 6.2 for numerous reasons.
Efforts are being made toward 7.1, but not there yet.

Anyway, the new Intel NICs are recognised by Centos 6.6 netinstall ISO when
booting, but not Centos 6.2. I have had the idea of unpacking the initrd
and using the e1000/e1000e drivers from 6.6, and updating the 6.2 initrd.
This has not worked so far, but I'm hoping I've missed a step.

I have:
1) unpacked both initrd's
2) updated modules.* from the 6.2 initrd to match 6.6 for the relevant
modules/dependent modules
3) updated the pci.ids file
4) chrooted, run `depmod -a -v`
5) rebuilt the initrd

6.2 still fails to see the NIC. Is there a step I've missed here? Do I have
to concern myself with the kernel(vmlinuz) file too?