They might be your only choice. Ditto "buy direct". I would also ask what new parts they install. For sure, new clutch plates and seals. Never been in one, but per photos in posts, it appears there are some large plastic parts inside so ask if replaced or how they know they won't later crack. In general, nylon has proven long-lived and transmissions and engines have used it for decades, so perhaps no concern.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans