How close is too close?

[SwitchbladeII]

I'm in the process of installing a bed tank and it's looks like the tailpipes and the fuel line are going to be close to the tank. Wondering if there is a spec on the safe distance. It's ironic the exhaust from the mufflers back was one of the few things on this truck which didn't need attention. As always any feedback and suggestions are welcome and appreciated.