The Porche

They cover the car because the guy they stole it from probably reported it stolen. Once that happens, the cops would probably remember it from the police station and figure out pretty quick that it was Lucas. Then the cops would search for the stolen Porsche, find it, find Lucas and perry and there is the end of the movie.

Speaking of the "Porche", is it possible for someone the size of Nolte to just "slide over" in the seat as Short insists?

The only thing wrong with that Porsche is that it's misspelled.