We might need to give this #18 fella a break. This is a 1960 Chevy Impala, nose to tail. And yes, it has a 1963 Chevy grille stuck in it (just because somebody had one laying around). As far as the wheelbase, many of these "vintage" cars use more modern, or recently used and out-dated underpinnings, and that usually means shorter wheelbases on the old "big" cars.
As Brian mentioned, vintage racing is a growing segment and we have a healthy contingent in central Illinois that race on dirt. The cars are cool looking and I applaud the racers that build and maintain them to entertain the crowds! I might start a thread just for vintage car photos to hopefully inspire someone to build something.