Are all Sidekicks and Tracker rear rearends 12 bolt or are some 10 bolt also? I have only looked at the ABS rears which have all been 12 bolt. The reason I ask is because I am thinking of buying an ARB and don't want to be locked out of some of the early low ratios like the 5.3 or 5.6 ?

Early diffs were 10 bolt, ARBs don't come that way, so you may have to
go another route like lockers, cost lots less too

Wild

Are all Sidekicks and Tracker rear rearends 12 bolt or are some 10 bolt also? I have only looked at the ABS rears which have all been 12 bolt. The reason I ask is because I am thinking of buying an ARB and don't want to be locked out of some of the early low ratios like the 5.3 or 5.6 ?

Sadly, the 5.83's have been unavailable for a long time.  When I die, I'm going to leave my 5.83's to somebody, I think.