The FX4R was an updated version of the FX4, introduced in the mid-1980s. The FX4R featured various improvements over its predecessor, including modifications to the interior, suspension, and safety features. It often came with a diesel engine for better fuel efficiency. Like its predecessors, the FX4R was designed to be wheelchair-accessible, addressing the need for inclusive transportation.

The FX4S was another variant of the FX4 model, introduced later than the FX4R. The FX4S included further refinements and updates to the design and features. It typically came equipped with a diesel engine, consistent with the trend towards more fuel-efficient options. Similar to previous models, efforts were made to maintain or enhance accessibility features.