There is also a roller that fits over the bushing and creates the gap for the sprocket tooth to slide into. It is 1 3/16" ID x 1 7/8" OD x 1 1/8" long.
The whole assembly is pinned with a 5/8" ID x 3 1/8" long CRS. This has 1/8" holes drilled back from each end 7/16" on center, to receive a cotter pin.
The sprocket bore will be up to you when you cut and bore it. On mine it is 2 1/2" which is too large. Also, the sprocket is 1" thick. If you choose to cut one from thinner stock, the bushings, rollers and pins will need to be shortened appropriately.