There is some stuff I'm certain about so i'll give you answers to that, but will mark stuff with a maybe otherwise:
1- I assume you are talking about an ae86 with factory powersteering? If so, you should be able to keep power steering pump and bracket from the ae86 and mount it to the 20v (providing clearance at the head area is not much different which should be fine and that you use a rwd 4age crank pulley for the correct belt offset)
2- If you go manual rack, I cant say a ke70 will fit but what I do know is the cross member has larger mounts for a power steering rack (manual rack is slimmer, however Im sure there are oversize bushing kits on the market that can sort this out for you). I know that you will also need a small shaft extension piece or a manual rack steering collumn, but I cant remember since its been a while since looking at this.
3- Pulleys... which ones? Crank pulley from the rwd 4age 16v as stated in 1 is required for the pws to line up. Water pump pulley from a rwd 16v 4age will work if you use a rwd water pump, otherwise fwd pump with fwd pulley from any fwd 4age will do (as long as correct pump is used with correct pulley, this will not change the line up to the crank pulley).