I prefer a depleted uranium block. They add substantial normal force to the front tires and provide for a very memorable spirited driving experience compared to lighter cylinder block alternatives.
An extra added attraction, available at no extra cost, is the pale blue glow the engine block adds to the ground immendiately below the nose of the car. This is extraordinarily helpful after leaving various establishments serving vision impairing beverages. The light blue glow provides proof positive as to where your vehicle is parked even in dark garages!
Ed