Not quite sure what you mean by "half-shaft seals". The only thing close to a seal in the double-u-jointed halfshaft assemblies is a felt ring at one end of the sliding splines. And even in a major crask and fire, those do not fail. Can you clarify your question a bit? What do the "seals" in question look like? If on the other hand, you meant "u-joint seals", and you have made-in-USA halfshafts, a Ford F-500 5-ton truck u-joint fits the commonly-used Spicer halfshafts.
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