Lengths of s13 axles

Ive put on the Z32 rear aluminum knuckles and when it came time to put the rear shafts in I realised I had no significant markings to tell me which one is which. To make it worse I have an extra set and before I start playing mix and match is there any easy way, including measuring length, to tell which side is which? Ive tried measuring exposed shaft segments but they all apear to be different. Must be because of where the boot was strapped down. They are all 6 bolt to the LSD. I did a search on the net and could only find info on 5 bolt. Any help would be great. Thanks.