And the secret to this was using the script correctly (--rename instead of --update)

interface-rename --rename eth0=3c:a8:2a:15:4a:9c

Name  MAC                PCI              ethN  Phys  SMBios                         Driver  Version  Firmware                 
eth0  3c:a8:2a:15:4a:9c  0000:02:00.0[0]  eth0  em1   Embedded LOM 1 Port 1          tg3     3.137    5719-v1.46 NCSI v1.5.12.0
eth1  3c:a8:2a:15:4a:9d  0000:02:00.1[0]  eth1  em2   Embedded LOM 1 Port 2          tg3     3.137    5719-v1.46 NCSI v1.5.12.0
eth2  3c:a8:2a:15:4a:9e  0000:02:00.2[0]  eth2  em3   Embedded LOM 1 Port 3          tg3     3.137    5719-v1.46 NCSI v1.5.12.0
eth3  3c:a8:2a:15:4a:9f  0000:02:00.3[0]  eth3  em4   Embedded LOM 1 Port 4          tg3     3.137    5719-v1.46 NCSI v1.5.12.0
eth4  38:ea:a7:12:de:14  0000:04:00.0[0]  eth4  em49  Embedded FlexibleLOM 1 Port 1  ixgbe   5.9.4    0x800009e0, 1.3089.0     
eth5  38:ea:a7:12:de:15  0000:04:00.1[0]  eth5  em50  Embedded FlexibleLOM 1 Port 2  ixgbe   5.9.4    0x800009e0, 1.3089.0 

All done.

@olivierlambert I've made the needed adjustment in the build script to override the default. Now I wait for another set of patches to test it.
Thanks all.

@olivierlambert Wow too easy. Thank you!

@olivierlambert I finally had a chance to apply patches to the two ProLiant servers with the 20 minute boot time and everything worked as expected.