The bend on the pipe for the rear cylinder is not the same. If there is any interference it will be with the sidecover. However the stock Sabre pipe crosses at a higher point than the stock Spirit pipe so putting a Spirit exhaust on a Sabre most likey will not cause an issue there. Were the switch going the other way there would probably be a need to change the side cover. All other mounting points are the same. It should be an easy swap.
Im grave digging. I ordered a sabre side cover today just to see if it will fit the spirit. Too many oeople have asked this question and i have yet to find a 100% true and correct answer. If anyone knows,please chine in,snd i will go ahead and order the pipes. Thanks