I've many friends who converted the E33A Super Saloon to 4WD and manage to pass both inspection and roadblocks. That was a few years ago.
Today, even some JPJ officers drive converted 4WD Wiras or Satrias but they got away with it.
So, if u convert... u may be lucky for a few years only. Do u really want to risk having your precious car confiscated by JPJ? I've seen many stranded (sita) 4WD Wiras and Satrias at JPJ Wangsa Maju.