Those old versions are tgz archives. Once extracted you can convert them to ova files with ovftool:
ovftool --allowAllExtraConfig --extraConfig:monitor_control.pseudo_perfctr=TRUE --extraConfig:timeTracker.forceMonotonicTTAT=TRUE --extraConfig:monitor_control.disable_tsc_offsetting=TRUE --extraConfig:monitor_control.disable_rdtscopt_bt=TRUE <path to>\DataONTAP.vmx DataONTAP.ova
8.3+ doesn't need all the extraConfig but older versions may panic without it.
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