Have 260K on '92 1.6 Auto 4x4 and it is getting tired. Looking for info on best engine upgrade. Thanks much.

That's a wide open question.  It all depends upon what you want to do with the truck. 

I am very satisfied with my 1.6 16V, of course I'm driving bone stock, mostly street driving, and light wheeling. It is probably the most economical and simple upgrade. 

If you have a machine shop, and can fabricate an adapter, the only limitations are time, money, imagination and the size of the engine compartment.  If you want to go for the really obtuse, a V4 (old Saab) or a flat 4 (Subaru Brat) might be fun, but probably not as reliable as the Zuk engines.

And, of course, if you ask a redneck, their answer to the engine swap question is always the same.  "Lest drop a 350 in 'er."

I'd go for the 1.6 16V Zuk.

Thanks jzap.
If I decide on the 1.6 and buy a used engine to rebuild in preparation for the swap are the Tracker/Sunrunner/Suzuki all the same?
Tks.

Sunrunner, Sidekick, Tracker should all be the same. 

I have heard that there may have been a change in the splines of the output shafts at some point in time.  I may be confusing that with axle shaft splines though.  I  am sure someone more knowledgible will chime in on this...

Yea, your thinking of the front axle shafts that switched from 22 spline to 26 spline in 96.  If you have a 92 1.6 it is most likely the 8 valve.  All 8 valve blocks are the same, but you will run into a couple of different intakes which may require you to swap out before dropping the new engine in.

Aftermarket 4x4 sells parts to help drop a 2.0L engine in the 1st Gen Tracker/Sidekick/Sunrunner/Vitaras.  You can read about it at http://members.cox.net/aftermarket4x4/2litertracker.html