The easiest way is to install one of those clear view fuel filters... if you notice a lot of rust in the filter then either your gas line needs to be replaced or the tank. If you drop the tank and drain the fuel you should be able to determine what kind of shape it is in.
If its the original tank, I would replace the tank and lines if your in the restoring mode. Its not that hard and not to expensive and that way you won't have to wonder later....why does my car keep starving of fuel?
My tank was in good shape, so just to be sure ther wasn't any small pinholes or rust, I got a tank sealer kit from Eastwood for like $30 bucks. It worked great and I have piece of mind without spending the dough for a new tank. Just another option.