So I used the same shaft which came with my engine. The problem is that since my shaft is the same length I bored out my sprocket to fit on the rear but now there's not enough shaft length to align the pulleys
I cheated and bought the DeathRow Converter on Ebay for $109. Looks like they mill the back side of the mounting plated so that the 10T sprocket can run on the back side. Either way- I cheated and do feel a minor amount of shame.