If you have a waste fire ignition, you need either double platinum plugs or platinum/iridium plugs. If you don't, the cylinders that have reverse voltage will have the plugs wear fast. The platinum tip needs to be on the firing side of the plug. The original plugs in such engines were usually single platinum, but half of the engine had the platinum button on the center electrode and the other half had the platinum button on the side wire. Using double platinum makes it "idiot proof" so that the plugs don't get installed on the wrong cylinders.
Platinum plugs, single tip, on engines that have all the cylinders fire with the same polarity, will last longer (much longer) than non platinum plugs. I don't remember what kind of plugs the dual plug Ranger uses, but I think it may be double platinum.