Pete (Nutrocker on the HAMB) has recently fabricated a twin plug conversion for his motor. I have had the pleasure of sharing the driving duties at a few hill climb events in the car and can tell you it goes really well on what is a pretty much a stock French flathead. Even if the second set of plugs don't make a difference they sure look great!
Here is a clip of the car in action.
https://www.youtube.com/watch?v=ku7HDD4g50k