Can these be changed?

I'd get the real u-joint kit from Borgeson. AFAIK that kit makes the shaft as long as it needs to be for the manual box. Not sure exactly which u-joint/coupler you need. Call Borgeson, they are the experts. http://www.borgeson.com/xcart/catalog/Steel_Vibration_Reducer_UJoint-orderby_0-p-1-c-17.html