Narrowing an 8 1/4"

Hey folks ! I'm looking to narrow my 8 1/4" diff by 1 1/2" . I've searched the FABO , Bigblockdart sites and the web in general to find out what the lengths are of the axle shafts for an 8 1/4" but wasn't able to find that information . I have read that the pinion shaft is offset by 1 3/8" to the passenger side ..... so I was wondering if I located another passenger side axle shaft to be used on the drivers side and narrowed the drivers side axle tube by 1 3/8" , does this seem doable ? Is there anything I'm over looking here ? I know it's not the 1 1/2" I was looking for but I would be happy with th 1 3/8" if it would work . My Dart Swinger is just going to be a cruiser with a bit of attitude .
Thank you in advance for your thoughts and your help ! Vince .