Can't find my manual just now. But in the early to mid-fifties, they dealt with a few design weaknesses involving the timing gears and the front cover. The timing gear would crack through the hub spokes. They made a wider gear including thicker spokes. They also changed
the front plate. They are in two different thicknesses. I think they made it thicker. Anyway,
it may have required a thinner gasket to keep things relative. There is a question in my mind whether the plate was to support the engine, or if the engine was to support the frame rails as they went from bell housing to front axle support.
It's a case of "not-quite-good-enough". A minor fix was tried. I think the camshaft and gear got a total remake later. The plate may have gotten strong enough, but the side rails did get stressed enough to loosen up. Come to think of it, they might have gotten thicker too.