From what I understand with those trunk pistons are they were later production replacements for the smaller original intended ones. Early '81 Montes had the smaller ones but failed cause of the weight of the trunk lid. Later fix was to install those to replace them. I'm thinking towards the end of the model year they were factory installed. One downside is those twist the hinge arms & causes stress wear on the bolts using the washers to cut circles into the lid making you think it's coming loose.
I swapped mine out to the smaller ones to have them fail.