The easiest way to tell a genuine Lamborghini from a replica car is to examine the vehicle's engine, as fake Lamborghini vehicles very rarely have a genuine Lamborghini engine installed. Examining the engine is facilitated by the glass engine enclosures used on many modern Lamborghini models.
Common donor cars for Lamborghini replicas are mass-market, mid-engine sports cars such as the Pontiac Fiero and Toyota MR2. These cars use a much smaller four-cylinder engine than the typical high-displacement V10 found in a genuine Lamborghini, so it is not difficult to tell a replica from a genuine car if it is possible to view the engine. While some replica makers may replace the engine from a donor car or use an original tube chassis and crate engine, it is rare to see a replica where the correct engine design is reproduced well-enough to pass an inspection.
Many Lamborghini replicas made from donor cars have different proportions as compared to a genuine Lamborghini. For example, the wheelbase of a 2014 Lamborghini Gallardo is approximately 100 inches, versus the 96-inch wheelbase of a 2005 Toyota MR2. Similarly, the width of a Gallardo is 75 inches, while an MR2 is only 67 inches wide. This leads to many replica cars having a squashed or stretched appearance, giving astute observers another way to differentiate a real Lamborghini from a replica vehicle.