When Tammy takes off to Vegas in 1971 and they are showing video of the Vegas strip, you clearly see a black 1984 Trans Am in the shot that appears to be made up as KITT from Knight Rider due to the unique tail light black outs that were used on the car.
When George and Tammy went to play in Las Vegas there is an opening scene showing the Las Vegas strip. The year being portrayed was supposed to be around 1971. However an early/mid 1980s Pontiac Firebird is seen driving down the strip.