I had a similar problem but not NM related when I
added two 1GB nics to a box that had a 100MB onboard nic.
I wanted the two 1GB nics to be eth0 and eth1 but
the onboard nic would always revert to eth0 on reboot.
I could bind them with system-config-network but could not
get them to stay ordered to my preference.
I added the aliases to modprobe.conf to solved this issue.
alias eth0 r8169
alias eth1 r8169
alias eth2 e100
Alan