From when the engine was first introduced on , what 1947 until they went to the more modern casting techniques over time, the engine really never changed. It may have gotten a bit heavier as they cast in more aluminum, and then added muffler ears and such. The flaws in the exhaust could probably be filled in with JB-Weld just for looks. I have welded broken exhausts with by TIG welding them with good success, but since there is no stress on the joint the JB-Weld may work OK. You could maybe even add on a longer exhaust stack that way also but forming it from sheel aluminum and making fit as tight as you can before applying the JB-Weld.
Type at you later,
Dan McEntee