I was able to it to work with 6.5 by reverting grub back to kernel version 2.6.32-358, doing a yum downgrade for the kernel-{headers,devel,firmware} rpms, and then editing a couple of files in the iso and building a new one. The diffs for those are
# diff iso1/distro iso2/distro
1c1
< rhel6.5
---
> rhel6.4
# diff iso1/mlnxofedinstall iso2/mlnxofedinstall
158a159
>
260,262d260
< } elsif ($dist_rpm =~ /redhat-release-.*-6.5|sl-release-6.5|centos-release-6-5/) {
< $DISTRO = "RHEL6.5";
< $rpm_distro = "rhel6u5";
654d651
< print "dist = $MLNX_OFED_DISTRO\ndist = $DISTRO\nrpmdist = $rpm_distro\n";
779,780c776
< if (($DISTRO eq "RHEL6.5" and $kernel !~ /2.6.32-358.*el6\.$arch/) or
< ($DISTRO eq "RHEL6.4" and $kernel !~ /2.6.32-358.*el6\.$arch/) or
---
> if (($DISTRO eq "RHEL6.4" and $kernel !~ /2.6.32-358.*el6\.$arch/) or
# diff iso1/mlnx_add_kernel_support.sh iso2/mlnx_add_kernel_support.sh
339,341d338
< redhat-release*-6.5*|centos-release-6-5*|sl-release-6.5*)
< distro=rhel6.5
< ;;