My Lincoln Mark VIII has excellent sleeper qualities. It looks like your typical car that grandma would drive to church, and alas it's typically used that way. But has a 280hp V8 that's basically the same engine that went on to be used in the Mustang Cobra. Runs very low 15's in the 1/4 mile. Not insanely fast, but enough to surprise the hell out of a lot of people.
My slightly modified '88 Thunderbird Turbo Coupe is a good sleeper too. I pissed off my boss when I outran his brand new Navigator with my old POS 4-banger. He just drove by with his middle finger in the air and never brought it up again.
matteo101, I emailed those pictures to a couple friends of mine. One loves Cadillacs, the other is a VW fanatic. They both got a kick out of it. Is there any info available with the details of the swap? The pics are cool but I'd like to read about what was involved.