use the stock s14 spacers on the main diff bolts. If you need a measurement or want to make a drive out to me I can give you some and full details on the swap.
s13 diffs just a bolt that goes to the subframe while s14 have diff mounts.
Put the spacers between the bolt and differential case.
you won't have an issue bolting it up, but if you were to do the opposite I would recommend these:
SPL Parts PRO Solid Differential Mounting Bushings S13
OR
you can use the worn out stock ones from a s14.