I believe that 1982 was the year before Helicomatic hubs and cassettes were introduced by Maillard, so if this were my bicycle and improved shifting was the priority, then I'd switch to a Shimano index compatible rear derailleur and one of their HyperGlide compatible, 6 speed freewheels and chains. The combination of slant parallelogram, CAD designed derailleur in combination with the profiled cogs and chain plates, makes a world of difference and the cost can be less than an era correct mid-range Huret. I'd keep the OEM rear derailleur, freewheel and chain, in case you decide to sell the bicycle in the future.