Is there an oil sending unit on a 1987 dodge ram charger?

Yes, a 1987 Dodge Ramcharger has an oil pressure sending unit. However, it might be combined with an oil pressure switch, or there might be separate units for a gauge and a warning light. You'll need to consult a wiring diagram or a parts diagram specific to your engine (e.g., 318, 360) to be certain of its location and configuration.