[Bob Bidonde]

This slide shows the original timing gear and the modern reproduction. In my opinion, the aluminum timing gear has superior strength, but I am not to keen on having an aluminum gear being driven by a steel gear for a galvanic reason. Also, I suspect that the aluminum gear will have a higher wear rate than the laminated gear.
The slide shows an original gear where its aluminum hub has separated from the fiber which is a common failure mode of original gears. I replace all original gears I come across with modern reproductions.
From experience, I have thousands of trouble free miles on Bratton's 8750 Laminated Timing Gear, so it is a proven excellent choice. If I were to hop up the engine in my A's, then I would consider the aluminum gear.
Bratton's 356B Aluminum Alloy Gear #8760 is the lesser expensive option. 356B Aluminum is for casting. The primary alloy in 356B Aluminum is silicone with smaller amounts of copper or magnesium. The "B" designation is for the purity of the cast material with an "A" being the highest. I do not know what the heat treatment for hardness is of Bratton's aluminum gear.