for starters,513 gears from a side kick are put into samurai 3rd housings,and they just don't bolt in ,you have to space the gears and use a ring plate to keep the pins in .side kick rear housing is in the middle (like a toy rear diff).zukes to the pass. side.find out what housings are under your zuke ,then you can trace gears and axles. there is no after market axles for zuke or side kick unless you get chrome ally axles.witch are the same just stronger.there are a lot of different gear ratios for both.counting gear ratios is easy.just see how much tour pinion output turns in relation with your wheel.if you got any pics of housings.post them.hope that helps .lock the rear and weld the front if you have locking hubs. cheers.
when in doubt hammer on it , if it breaks it was no good to begin with .