A plain and simple bed from IKEA was made to look like a car bed using vinyl cutouts. The bed used is the Vikare bed (which is no longer manufactured). Finding an inexpensive and simple bed is fairly easy - check IKEA, thrift stores, garage sales and amazon.
The "grill" and "headlights" are made of black contact paper or vinyl. Add a license plate for additional fun. Via here originally from here.
Con-Tact Brand Covering Cover Contact Paper, Black Name Embossed License Plate"Whistler Junior Loft Twin Bed, White DaVinci Modena Toddler Bed