I'm not 100% sure of this but I remember someone telling me that the SLS was optional (but almost always installed) on non US wagons but was standard on US wagons. That doesn't mean there wasn't a wagon or two that made it to the US without SLS but it suggests that they would be very rare and unlikely many if any dealers would carry parts for the conventional setup. For those that wish to explore a factory conversion I'd suggest they look abroad, especially places where the simpler setup might be favored.

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LRG
1987 300D Turbo 175K
2006 Toyota Prius, efficent but no soul
1985 300 TDT(130K miles of trouble free motoring)now sold