There was a narrower spline area on the aluminum shafts on the sprocket side in the 2018s so if running a belt drive it would need a different bottom hub. On the 2019+ they went back to full-width splines like the 2012-2017 had so should be good there. Brake side use the clip off the 2012. I originally thought there might be an offset difference since they changed brake caliper part numbers in 2018 on the aluminum shaft models, but guys were putting the aluminum shafts in without changing calipers. Hillclimb guys were also running steel shafts for durability. I'd say put the old shaft in with the new brake and if everything seems to line up run it. Should be a quick check. If you have to squeeze the tunnel together a little bit to get the snap ring on the brake side that's normal.