The gears I have replaced in the past are gears that are worn pretty near a knife edge. Those gears on your distributor are in good shape.
Also keep in mind that the gear is pinned on the shaft when it was made. Not a big deal, but you will have to grind off the head, knock it through, and source a replacement roll pin.
The 2403 distributor entered service for the 55 model year and was used up through 63. The gear for the 2403 on a cast camshaft is 1929578. The earlier gear for the steel cam motors is 1865180.
The 1929578 gear comes up on eBay with some regularity so if you want a new gear and can hold out, you might find one there. I am certain there are other gears, as noted in the prior posts, that might be candidates. Back in the early 80s, when vertex was still in blue bell pa, I bought a rebuilt vertex for one of my 235 motors. They used a distributor gear for something, only had to redrill the pin hole so likely other gears can be made to work.
