The trick to installing a ZX tank on the S-chassis is to use a heat gun. You can soften the plastic and re-form the tank to clear the right front cooler. It is VERY important to take your time heating up the tank. It will take a little trial and error, but you will discover at what temp you can soften the plastic enough to mold it, and allow it to cool to the shape that you want. DON'T get it too hot! Once tank and console are installed, there will be a slight gap between the console and rear edge of the S hood. I made a crescent-moon shaped piece of black plastic to fill this void, pip-riveting it in place onto the front edge of console. To locate either side of the tank, I also welded on some small brackets on the steering hoop to locate the tank side-to-side. I made a bracket for the rear of the tank, to clear the heat exchangers as well.
I did this to my "Mutt" 670, and the ZX tank, console cover, and ZX seat look factory. Over four years later and no problems at all.
With a little time and effort, it WILL work!