Parker 1973

Here are a few shots from Mercury's photo files. I have over 100 more from several races.

What is the contraption sticking out the side of the towers of power, custom exhaust?

Those engines are Twister 1's. They came that way from the factory. That was the engine that came after the 125 Super BP Stacker. It dumped the exhaust down the side into the mid and was a lot quieter than the stackers. Still a 3 carb motor. They were around 160HP. The T2's running with them were 6 carb inlines. Quite a bit more HP.