MK3 rack will fit, but tyou'll need to change the track rods for MK2 PAS ones, and fit the MK3 UJ

I would take off all the pas pipes, pump and alternator setup off it as well and fit em all to the MK2. the pipe from the pump to the reservoir wont fit the MK2, but that one is just plain rubber hose anyway so old one should be fine. pump -> rack hose is direct fit, the rack->reservoir hose will fit after you cut the rubber end down a bit.
all the pas pump and alt setup will swap over from the MK3 as well, but have to swap it all as a complete set inc all brackets and pullies