You could get RHD A-Body Barracudas for the UK market directly from Chrysler and RHD Mopars were sold in South Africa, Australia etc. I'm pretty sure a 4 speed must have been avaialble in some of those, though not sure they were available in the UK (attched article say a 3 spd was available in one fitment, but not a muscle car)
https://www.allpar.com/threads/chrysler-uk-united-kingdom-a-history-of-chrysler-in-britain.229666/