The Stovebolt Site Forums The Shop Area Driveline Tranny won't go into reverse (SM420?)

So if I gathered right, the "crash box" is unsynchronized. Mine gets a bit annoying because of grinding gears. From a complete stop in neutral then shifting to first, I get a "mild" grinding. 2nd and 3rd may or may not grind depending on engine revs. or truck speed. Is this normal? It is not the original transmission but looks and fits like the original to my '54 235.