Running Fuel Lines

Where is the best place to run fuel lines, inside the frame our outside the frame? Mostly a street car but if I go to the odd race I don't want to run into tech problems.

I was told by a Tec guy, if you run them on the outside they need to go thru a metal tube where
the flywheel is. Plz correct me if i'm wrong.....

Running the brake/fuel/battery lines Inboard of the frame rails (facing the spinney/rotatey things) is always less desirable than running them outboard of the frame rails. But running them "inside" (as in actually being inside-of the actual frame box/tube structure) is always the best idea if possible.

Also don't forget to route any fuel/brake/battery lines away from moving suspension components (like shocks/springs/struts/etc) that might grab/pinch/crush said lines.