I need to replace the lines so anyone out there have a how-to followed by a recommended brand or supplier for the correct line? I'd like to keep it stock looking if at all possible.

Pelican has an article for replacing the lines in the tunnel.

Pelican sells the right size and material. Make sure you use the correct fuel injector hose clamps. They have solid bands.

3/8" Mild Steel, available at any Hot Rod FLAPS...

2-OH!

I just ordered a 20' roll of 5/16" stainless steel from Summit. 40 bucks delivered.

Two 5' lengths of 5/16" steel brake lines work perfect. Making the bends in the front of the tunnel is the tough part.

I recently replaced the leaky stock fuel lines on my -6. This was a piece of cake with the engine/tranny out of the car. Don't know if this is possible with the engine still in, but I made the 45 degree bends at the gas tank ends before I put the tubing into the tunnel. I then snaked the tubing past wiring and brake lines and out of the two holes in the front of the tunnel. I angled the front of the tubing the way I wanted it and then marked an X on the back end of the tubing on the side where I needed the right angle bend in the engine compartment. I withdrew the tubing just enough to get a pipe bender on it and bent the 90 degree bends. I re inserted the tubes all the way in and put the grommets on both ends (lube up the grommets with glycerin). It was easier than I expected, but like I said the engine was out of the car.