I have just found a pretty nice Easter egg in GTA V that relates to GTA IV and its vehicles.
Basically, there are two wrecks at a place called ''Thompson Scrapyard'' that both of which were drivable cars in GTA IV.
There might be more cars like this but at the moment I've only found the following two:
The wreckage found at Thomson Scrapyard: http://prod.cloud.ro...pZINz1A/0_0.jpg
The car from GTA IV: http://images3.wikia...-GTA4-front.jpg