[Mr. T]

If the vin# on the engine stamp pad, or in some cases down by the oil filter (rough casting) matches the car vin# located under the windshield, it "could" be an SS 396 (L34).
Other areas would have to be considered like rear multileafs, correct engine mounts (taller one on driver's side), big-block transmission crossmember, 3/8" fuel line, matching vin# on tranny, etc, in order for it to have a chance of being an SS.
An RS it is not. There are no back-up lights and the car has the standard tailights. The car does have the correct grill, but the areas around the hide-a-way headlights are not painted to match the color of the car, in this case Daytona Yellow - 76.
Looks like an aftermarket hide-a-way headlight/grill combination. Seems funny to paint an entire car, without painting around the grill and headlight doors.