Pretty great, if Chris Harris and the folks at Drive are to be believed.

This 1956 250 Tour de France's engine is pushing out something around 240 and 270 horsepower and it weighs about a ton, so it's at least somewhat quick. Certainly it was quick enough for the dirt roads this used to race on, so common for continental Europe back in the mid '50s. I can imagine this thing as a turbo Miata with really soft suspension and really bad brakes, but that's missing something.

Just listen to all the very expensive, very tiny parts in that three-liter V12 roar away, and stare at the depth of that paint, or the quality of the way-too-big steering wheel. THen you'll get close.