I have two older Exmark 48" walkbehinds w/13 HP Kaw. I guess they were made before there were models like metro and viking. Other than an occasional belt or flat have had no problems with either mower. I am buying a ZTR to begin next season but will still need to use a wb on some jobs and I want to keep both in service. 1. Has anyone made modifications to any mowers like these to make them perform better, without compromising the life of the mower? 2. Can you change the pulley size to speed up the blades? 3. What can I do to preserve these antiques other than taking them out of service?