[CentOS] upgrade dhcpd failover set from centos 5.x ->7.x

Is there a less drastic way to upgrade a pair of dhcpd servers on
Centos 5.x than forklifting the old boxes out and hoping the
replacements work?.   The failover protocol seems to be incompatible
so I just upgrade one at a time....  Has anyone been through this with
a clever solution - like compiling a new dhcpd on the old boxes for an
easy rollback?

-- 
   Les Mikesell
      lesmikesell at gmail.com