I would search for a transmission out of a "cloud car". There are a few that you can have a direct swap, from a 97-99 Chrylser Sebring base, 98-99 Dodge Avenger, Dodge Stratus too. If you want to do some things to improve and move away from the NV-350, you can.
Although by most accounts they can stand a lot of abuse... I say just keep it, rebuild it and go on with life.
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