hi
The long bolts are used to hold on the front section of the fully enclosed rear chainguard
If its not fitted then you need the short type
As said the bolts are shouldered to allow the plate room to slide
Quite often the case will be damaged by a PO over tightening the bolts and the the shoulders will have sunk into the alloy !! This needs to be fixed to allow the plate to slide
New repro plates *** oil between the two parts
run some sealer around the vee groove to cure this
John