That is an Awesome deal! Almost TOO awesome!
Okay, here is the cautionary message:
I am making a semi-solid assumption that the Sierra is not so incredibly different from the American SJ413 - especially in the floorpan. Nor is the swb Mk I Vitara. Yes, I am a Yank...
That statement out of the way, I have swapped out my '88 SJ seats for MkI swb Sidekick/Tracker/Vitara with little difficulty. They are superior in comfort, not hard to find and not too wide for fitment. Unfortunately, some Vit seats are a bit garish-looking (mine are gray with pink center trim) so you might be a picky chooser in your search at the wrecking yard. On the downside, Vitara seats sit an inch higher. This might cause difficulties viewing overhead traffic lights when you are first in line at an intersection and the driver is much taller than 5'9" ( 175 cm)
Here is a swap post:
http://www2.izook.com/?page_id=279I hope that this helps!