If your 1970 Superior is a commercial chassis car, then it should have the high windshield. Since the 1969 and the 1970 commercial chassis cars used the same windshield, and all the commercial chassis builders used the same windshields for identical years, that means that GM only produced 2 windshields for those years. The commercial windshield, and the passenger car windshield. I suggest that you take a measurement at the side of each windshield, and see how much difference in inches between the two. Now, if your 1970 Superior is a Pontiac low top vehicle, Superior might have used the standard car windshield instead of a commercial chassis windshield. If there is a difference in the windshield, then there is also a difference in the vent and / or the front door glass. If it is a Cadillac, I believe that Superior only used commercial chassis glass in them. Keep in mind, that the windshield pillars were welded onto the cowl at the Superior assembly plant, and they could have deviated from the normal procedure if there was a request from a customer. Please post some frontal views of the two cars.
thanks Paul