How could fuel lines be run down the tunnel?
 

In my '75 hot rod someone ran the lines (feed and return) down the tunnel......inside the boxed reinforcements in the top corners of the tunnel (one line on each side, inside the box). Is that normal? I want/need to weld on that area (yes I saw recent posts about that). I am wondering if moving them down to just lay in the tunnel is better??

On my '74, both feed and return are run down the driver side thru a "tunnel within the tunnel".

Yeah, both should be on top side of drivers tunnel.