My recently purchased 73 was a standard coupe from factory with open differential. Found and bought what I was told was a 73 z28 posi with 3:73 gears in excellent shape. Had a shop set up to swap em and mech said the z differential was 1 inch wider not to mention I was told by seller in excellent shape just need to drop in. Axles were bad. Did they make different width rear ends in 73? Could he have measured wrong? Maybe not a 73 z rear end? Mech said the posi and gears looked real good though and suggested I find someone to swap out posi and use everything else including axles out of my open rear end. Is this a good idea?? Don't want to dump more money int the rear that wont work.