The one in the song is a V8. I remember seeing a yellow Model A with a Lincoln OHV V8 that claimed to be the one the song was written about but I guess the guy who wrote the song would know.
"It's got a Lincoln motor and it's really souped up
That a Model A body makes it look like a pup
It's got eight cylinders and uses 'em all
Got overdrive, just won't stall"