Lionel has made at least THREE versions of the RS-3.
The first had a stamped metal frame, plastic trucks, and 2 truck mounted CAN motors. These only had the horn, headlights, and reverse board in the shell.
The second is the real cheapie you describe, with the plastic everything. These are mostly found in the cheapest of the starter sets.
Finally are the LionChief Plus class of RS-3. These return the stamped steel frame, but also have die-cast trucks, fuel tank, and pilots, vertically mounted flywheel-equipped CAN motors, digital sound system, and fan-driven smoke unit.
Unfortunately, the die-cast trucks are EMD Bloomberg trucks which are improperly sized for the loco, so that the mounting steps and pilots jut out beyond the frame... an OSHA no-no.
Jon 
