The case half is needed for the crank trigger, since the cam sensor is eliminated. You also need it so you don’t have a big hole where the oil pump “snout” sticks through to engage the gear on the crank pinion shaft.
The crank sensor triggers from raised spots on the flywheel, which the ecm uses to fire the coil. The firing pattern is much different from CPS to the CKP, so the new ECM is needed. Since the new ECM (DDFI-3) has many more pins that the old one (DDFI-2), your plugs won’t work. And if you are in the middle of the plunge it’s probably easier to replace the harness than mod it.
There will likely be someone with advanced DDFI skills and knowledge who may be able to make the DDFI-2 ECM and harness work with the CKP, but now we’re really going down the rabbit hole.
My suggestion is to stick with the 2007 pump and bronze gear. The oil pump was redesigned at that point and was used on the Sportster ‘til the end. They never did use the bronze gear, though.
Hammer performance has a YouTube video where they show the difference in the oil pumps, and if you dig around the World Wide Web long enough you’ll probably find the Harley tech sheet that shows the difference between the two.
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