Tar-like undercoating on 63 Valiant...any way to remove it?

Fuel line off, first coat of Goo Gone left on a few hours and scraped. Ugh...new fuel pump, hard lines cleaned out from carb to fuel pump, as well as new fuel hoses, clamps and filter. Second coat of Goo Gone on. Letting it set overnight, see if it'll soak through the thicker coating. Found some rust the undercoating was hiding, it probably did more to trap moisture than actually prevent it...