Roadster 3.7 evolution is not documented too well time wise. I would avoid pre 2015 versions though due to possibility of rev hang which mysteriously disappeared in later production. I say this as it seems MMC never officially recognised it in its worst form, although an alternate ECU was made available for a while at considerable cost to customers.

Around the same time the drivers footwell, on rhd cars at least, had the bulkhead width increased to form a cavity to better accommodate your right foot. See below showing outside of same taking up full width to bonnet catch.

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In August 2018 a narrower handed gearbox cover was used with multiple bends in the sides to hug the large gearbox, benefiting driver and passenger footwells.

Perhaps the biggest improvement was the entirely new five link rear coil sprung suspension introduced in April 2018. Brackets welded to the live axle accommodated parallel trailing links above and below axle and each side, with a diagonal panhard rod for lateral location. Coil over dampers provided the actual suspension medium. This was a huge improvement in axle location over the leaf spring setup which in its earliest form employed just one trailing arm as a sop to the massive torque from the Cyclone engine. So much so SSL offer a retro fit version to convert leaf spring models.

A easy fix to the very heavy clutch action on earlier models was to simply remove the pedal mounted return spring. It's simply not needed as eventually recognised by MMC some time before 2018.