They may need cut off a little. Since the belts are new they should be the same length. You don't have to remove the belts to cut off and resplice.
A couple years ago I respliced the belts on a round baler cutting a couple inches off. I put Alligator Rivet Fasteners back. Not a bad job as the belts don't have to be removed. Just make sure you get each end square and take a punch and get the rivets braded well.