As far away as you can get it. And put a heat shield in between.
After shut-down, they'll heat-soak and the fuel will vapor-lock. This makes for hard starting if you intend to restart shortly, such as after a fuel stop.
And even a double-layer of fire sleeve isn't enough to prevent this.
It's not an in-flight issue because at that point the fuel passing through the line cools it.
Dave
