[Jac Mac]

You have a one piece eccentric--you have been supplied with a cam equipped with a short dowel that is intended for a two piece eccentric ( tang type ).

Remove that dowel--usually a large set of side cutter pliers will suffice, using the gear spigot of the cam for leverage.

Buy & fit the correct (longer) dowel.

Clean the gear retaining bolt threads along with those in the cam ( check the length of that bolt to ensure it is not to long along with the correct thread--- some later cams use a 7/16 thread rather than 3/8 IIRC.

The single piece eccentric also uses a thick washer that prevents the dowel moving forward once all fitted up. A drop of loctite on the bolt thread when finally fitted & torqued to 36 ft/lb is good insurance.

The gear set for a two piece eccentric usually has a raised lip in center that allows the outer ring to turn freely once fitted.