The PTO was a drive though from the input shaft, so it was on the back of the transfer case. It was never offered in Australia. I have seen photos of early Japanese cars (typically SJ30's) with various PTO attachments. However, as the transfer case input gear was unique to the PTO version, using it with aftermarket transfer gears would be impossible. (well, without an impractical amount of work and cost) It appears they are really only used with the 1.0 litre case.
here's a photo and an exploded daigram (which doesn't clearly show the relationship between the PTO and the transfer case input gear):
Personally, I don't really get the appeal of a PTO winch on a Sierra. The only readily available PTO winch (Thomas) is enormous and very heavy. I don't know what the torque rating of the Sierra PTO is, but it would be fairly low - the shaft out the back of the transfer is pretty small diameter where it drives through the bearing, and on top of that, the PTO can't be used to winch the car back onto it's wheels or out of deep water because they're two places the engine won't be running. Even on steep enough hills a carby sierra engine won't run well at all to support winching.
I completely understand a PTO in a heavy, typically mechanical diesel "working" 4WD, but how much winchching do you envisage doing?