For a neater heater line install a variation on the upper coolant hose would be hard lines with flexible connectors at each end. Drop the lines down to the frame and then back to near firewall and back up (or if starting new bring them in at the kick board). A Model A frame doesn't leave much room, but getting a majority of the tubing down low helps the line of sight. Especially effective if the tubing could be routed under the headers, say along the oil pan rail, but again, depends on space.