If they are indeed shoulder bolts like the picture I posted they are a standard type of fastener. No need to go buying entire crankshafts. FCA doesn't make fasteners, they buy them from specialty manufacturers.

You need the diameter of the threaded part, the thread pitch, the diameter of the shoulder and the length of the shoulder from its end to the bottom of the bolt head. I'd start with Fastenal.

https://www.fastenal.com/content/product_specifications/STRIP.BO.pdf

This is just the first one that popped up. I'm sure they make hex head shoulder bolts. All available in both standard and metric sizes.

R.