Hey all
I recently picked up a cheap 89 Sierra with a Vitara engine that’s got a shattered driveshaft that needs replacing. Im a bit of a mechanic novice, so was after some advice on a few things while I make a plan to sort it all out.
1)     Does anyone one (see pics 1 and 2) know by sight what model the vitara engine is and/or how to ID this/ where to look to confirm? 

2)     Can anyone confirm 100% that it’s a Sierra gearbox that’s in there currently? (see pics 3 and 4)

3)     Could the Vitara v6 engine working with the Sierra box have caused the drive shaft failure? As in, the engine being too powerful for the box? The seller told me that it had been in there for a year or so with no issues up to the big bang point

4)     If (3) could be the case, is it possible/ what would roughly be involved in fitting a Vitara gearbox/ drive shaft to the Sierra- other running gear that would need changing/ modifying chasis/ mounts etc? Or is there other, simplier mods (different clutch etc) that could be done to strengthen up the box and avoid big bang #2?

Cheers in advance for any advice anyone could help out with!

The engine looks like it could be a 1.6 liter 16v model.  Attached photo show the engine identification stamping from a 1995 North American Geo Tracker.  It is located on the left side (exhaust manifold) of the engine where the transmission mates to the engine.  Note the G16, first 3 digits in the small stamping.