[Oldsguy]

If you think or suspect that the lines are damaged or are rusty then yes. You may be able to attach an electric pump (fairly cheap) on the end of the lines where the tank would be running to a jerry can of new fuel and pump that through the lines up to the mechanical pump. Disconnect the line at the inlet of the mechanical pump and then observe what comes out, especially in the first few moments. If the fuel is clean with no tinge of red or rust then you probably don't have any worries. Since you will be under the vehicle to remove the tank and clean it out do a thorough inspection of the lines for kinks and crimps too, probably before you flush them. I had to r/r the fuel lines and the brake lines on my '46 project and it isn't an easy task, measure, bend and fit, measure, bend and fit, all the while having sixty year old dirt and crap falling all over you.