if it's a 1997 SV420 it WILL be 26 spline & 12 bolt
if you do end up going down the track of fitting lockers to the 5.12's you pick up, you'll buy the locker to suit the spline count in the front so RD88 or RD208 from memory & the rear you'll buy it to suit what ever crown wheel you end up with 10 or 12, can't remember the arb part number for the rear & personally i'd look for a 12 bolt rear as the 10 bolts are getting old.
:EDIT: if you want a bolt in option, you will need to get the 5.12's out of a 1.6 vitara with the same shape dashboard as yours, (SE416 typeIII's are the last of the 1.6 aus delivered vits had the nice round dashboard & 26 spline front) all LWB's had the 12 bolt rear from memory, the update was late 1995-96 onwards.