hi,
i have just put the G16a carb engine in my SJ without an adapter plate! dunno where you are but lots of ppl in the Uk swear by not using a plate.
went in ok actually... the main point is that you have to re-drill the gearbox holes in the engine! make the top two bigger and relocate the bottom two. also make sure you get the top bolts from the G16a as the SJ ones are too small!
make sure you have the skinnier starter motor or grind some of the fatter starter casing off.
you will also need to relocate/adjust one of the engine mounts. its the driver side one on my sj (the side with the starter on it)
i have no lift so i've had to change the sump. its quite easy but you have to alter the oil pickup pipe bracket.
one random thing i found was that the engine/gearbox are now further forward (???) so i had to put a prop spacer inline with the gearbox>transferbox propshaft
anyway, best of luck! also the links below may help
Difflock :: View topic - 1600 conversion write up for you lot.
Difflock :: View topic - 1600 into sj without a conversion plate
final note: if you can, try and find a skinners union (SU) carb and make yourself an adapter/custom manifold. if you have a 1600 and SU carb it will go like **** off a shovel!