In my experience, the CENTER BORE on the 1993 Alfa Romeo 164 is 58.1mm. Based on fitting 1993 Alfa Romeo 164 Speedline factory alloy wheels to a Citroen CX, which has Center Bore 58.1 PCD 5x98 also. They slot right on. This explains why Alfa message boards note that 164 wheels are difficult to remove from 75/Milano models (CENTER BORE 58.6mm). They have found the tight fitment when a 58.1 wheel is mounted onto a 58.6 hub.