Carl H and Myself both know for a fact that teh HICAS one WILL work with a non hicas 91-94....
Just get a vaccum cap and cap off one of the return bungs on the bottom of the pump and cut the two wires off the cap itself (they are used for the hicas warning light) Then just go ahead and bolt the reservoir onto your driver shock tower, and attach the small rubber return hose to the reservoir. you can also at this time attach the hose from teh reservoir to the pump itself but dont attach to the pump.
Im going to assume at this point that you have the p/s pump sitting in front of you somewhere you can work on it. Clean it so you dont get too dirty, and even better to wear a pair of latex gloves. Unbolt the 4 small bolts on teh back end of teh pump (opposite the pulley) and pull teh back of the pump STRAIGHT off. It will come off, if not then wiggle it around a bit to get it to slide off. Inside you will see the hicas pump wheel and it will have 9 or 10 small square impeller plates. Remove these tiny plates and dispose of if you dont plan on putting back to hicas functionability.
Do everything you possibly can to block off/cap off the rear outlet (used for the hicas line) Easiest thing to do if you can find one (I couldnt) is a 12mm standard threaded pipe plug and some JB Weld or Loctite industrial thread lock. This si the most important part because i rushed this step and ended up wasting over half a large bottle of synthetic p/s fluid from the leaks. MAKE SURE MAKE SURE MAKE SURE you seal off teh rear outlet tight and solid. I cant stress it enough!
After that, just go ahead and reinstall the p/s pump the same way you took it apart, short of putting those little square impeller plates back in.
Go back to your car and mount the ps pump to your engine block, install the p/s belt, tighten the belt and then install the feed line from teh reservoir to the pump and finally twist the p/s line to the front outlet and mount to teh pump, placing one of the nylon washers on either side of the p/s line (you should know what im talking about when you see it). Torque down the stud to hold the p/s line to the pump (hand tight was enough to not leak on mine)
Fill the reservoir with your p/s fluid of choice, i like the full synthetic, makes the older p/s system feel newer and also has stop leak additives in it. Turn on your car and turn the wheel full right to bump stop and tap teh bump stop 3 or 4 times, then turn full left to bump and tap teh bump 3 or 4 times. Return to center and turn off teh car. Check your p/s fluid level and fill as required. repeat the bump stop steps to be sure to properly fill your steering rack. Cap the reservoir and shut your hood. You now have power steering on a non-hicas sr using a hicas pump and reservoir.
Added bonus: the SR Hicas reservoir is teh nicest looking one available out of the 4 you can use.....