2" body lift and 1 1/2 coil spacers should get you there.
first pardon for my poor English .
I do not agree that 2" body-lift with some spacers under the coil springs are enough to install 31" tires. maybe to install them - but not to drive this way .
first of all 31" tires on the original rim (without off-set ) will touch the body when You turn the steering wheel max to one of it's sides (You can fix it by limit  the wheel cycle  too - but off-set rim is the best and the rigth solution for it ) .
2nd - I don't know the English word for it - but if You put only spacers onder the coils You damage the distance  that the axle is able to open . it is more vital in the rear . ÂÂ
I advice to change in the rear for shocks that max open 53cm (original is around 47cm)  and in the front to add spacers under the struts .
92 Geo Tracker is the same as Sidekick 92 ?  if so it has (the injection model ) 80HP and 3 gears in the automatic model (if You don't have manual gears ) - this configuration is not ideal for 31" , You will feel that the car is carriage without a horse  .
if You have automatic  gear You can swap the RING & PINION GEARS in both front and back differentials with manual gear car from a junk-yard(I'm talking about the short model 3 doors only.  manual model 92 sidekick 3 doors pinion - corona/ring is 1:5.125 and auto is 1:4.62  ) or to buy from calmini
http://www.puresuzuki.com/Ring%20&%20Pinion.htm .
and one more important  issue - without changing the lower RING & PINION  as I adviced You will harm the rock-crawling ability of Your car - I mean first gear in LOW will not be short enough .
so my advice if You want 31" tires - the cheapest solution is :
4 spacers under coils .
2 spacers under struts
2 new longer rear shocks (the rear shocks are much cheaper then the struts - and they are standard)
some body lift .
Sincerely
HitRick