[vettestr]

You have several options as to type of fuel line with cost, your ability to install and performance being main factors. You must also consider location- routing and safety in your choice.

You want to run on the inner side of main frame tube, not the bottom so a jack could crush or road debris will damage it. Think about protection from a failed u-joint or drive shaft failure and exhaust heat when routing. Avoid multiple connections as they are each another leak potential. Large diameter is better than too small and sharp or numerous bends decrease flow potential also a concern for return line to keep the back-pressure low.

Any choice will need connections from clamps to compression, flare or inverted flare could be used. I like annealed 3/8' steel tube in 20 foot rolls for main feed and return. It requires a flare to connect many fittings or adapters but it is not that tough with the correct quality tool and a little patience. Hose in rubber to teflon lined to stainless steel braided fuel hose kits are another option with varied connection types. Hard or ridged steel brake lines get very tough to bend when diameter needed is used, good luck there.
Aluminum is easy to bend but I think is weak against corrosion. Moisture and alky in gas in aluminum lines just do not work for me over the years. I know there are many who have had good results but I am not one of them.