In the Service Parts List the number of packing shims for the windscreen side posts is specified as "A/R" (as required). I believe the car was designed to use nominally one shim each side (two total). With production variations in the car bodies and windscreen assemblies the number of shims required could vary from 0 to 2 each side (0, 1, 2, 3 or 4 total). My car incidentally assembles nicely with no shims, but don't bet on it. If your car needs the shims and you leave them out the result could be distorted windscreen and possibly broken glass.

During installation, drop the screen assembly into place and see if it will wiggle slightly from side to side. If so, then insert a shim on one side on the outboard side of the post and try it again. If it still wiggles, insert another shim on the other side and try it again. Stuff in as many shims as you can get to fit in the space allowed without forcing it. Then when you tighten the mounting bolts you will have the least amount of distortion and stress on the assembly.