Lang,I think the length of the rear door lock stick is shorter than that of a front door.I know that the tip of the stick is narrower as well.I wouldn't modify the latch mechanism.Why not post an add in the wanted section for the panel truck rear barn door lock.
The stick has to be placed into the right position on the lock as well.If it's not,it will not lock and unlock the lock mechanism.I would bet the original style stick will fit your reproduction lock.I will look for photos of mine and try to get them posted for you.
Tim
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