These two pages might be able to give you some comparative data.
http://www.trainweb.org/galt-stn/cproster/locomotive/1600s/1600.htm
http://www.trainweb.org/galt-stn/cproster/locomotive/8500s/8500a.htm
i have seen pictures of CPR converted geeps and i was wondering what were the main spotting differences between GP9's and GP9u's?