Hey Fred... JB Weld is probably the right approach and with a little ingenuity you can lick the offset expanding crack problem . First clean the inside of the part on both sides of the crack of any paint or grease, and warm the part to close the crack ; next - drill several 3/32" holes on 1" centers about 1/2" away from the crack on both sides of the crack; then - with some 1/16" dia. annealed stove pipe wire,cut some 6" lengths and lace it diagonally to form some wire "X"s ; fit them into the drilled holes from the inside of the bowl ( bridging the crack , and draw the crack snugly closed ) . With the excess ends of the wire now lightly twisted together on the outside of the bowl , mix up some JB Weld and tack-bond the "X"s in place inside the bowl. When that has set... snip the wires as close as you can at the outside of the bowl; mix some more JB and carefully fill around the ends of the wires where they exit the bowl surface. After the JB thoroughly cures you can file the wire ends to blend to the bowl surface ; grind or file the crack to a 1/8" "V" , fill with JB Weld ; and dress the surface after cure. You're now ready to prime and proceed with finish paint prep. This whole operation might take a couple of days in drying time...but not much more than an hour , or so , in working time ! Once you've done it you can apply the same system to lots of restoration applications ! ( You'll be saving taillight housings , heater shrouds, and all sorts of goodies .... bb