I agree w/ blazin,
the 81-7 had a bolt on cowl cover and had to extend the wiper arm studs so the could have clearance.What you mey need to do is go to a junkyard and look for a complete wiper arm assembly unit from a 1973-1980 style truck that has the shorter stubbies and bolt it in.But look at the cowl i think the 81-7 drivers side wiper arm assembly was 3 bolts and the 1973-1980 are 2 bolts that hold it into place if you got a 3 bolt setup you got the newer setup. You`ll just have to either weld up the holes and drill new ones for the wiper arm assembly, and you may have to do the same for the pass side arm assembly as well.
thanks
pat