Well... Definitely put it where the sun don't shine!
It looks like the best place would be in the fuel line as it goes up just inside the rear frame kickup, just behind the rear bulkhead. The switch control could extend through the bulkhead behind the driver's seat. At this point, it's going to be a bit tight working in there, but it looks like your best bet. This installation will be the mirror image of my recommended location for the battery cutoff switch.
I haven't seen us do any switches like this, so I can't recommend any particular brand.