All cars with a chopped top have custom made windshields. The glass guy takes a pattern from the surround and then cuts one to fit.
The other windows in the car are also cut to fit. In some cases where the windshield has a curve to it, the glass guy can do 3 things. Either run a split windshield with a partition down the center like in some of the 40's cars, split the windshield and bevel both sides to match as a seamless one piece windshield or actually get a curved piece of glass the will fit.