I just went through this on my 91 318is (airbag car) and will write about it with some pics in my profile thread. I have a 95 e36 m3 rack, but should be physically the same as all the other e36 ones. First, you can use the e30 tie rods or use e36 ones. I used e36 ones as they are beefier. Second, you will need spacers when you bolt rack to the subframe. You can use washers or buy a set pre-made. I bought mine from AKG. Someone on e30tech sells them cheaper. Next comes to the firewall plate. In my case, the steering sharft that goes from the knuckle into the steering wheel came out with my rack and knucle. I guess the 32mm nut under the steering wheel was not tight. This made the install more dificult as with the e36 rack the orientation of where the spindle connects is off and make the shaft move over and hit the firewall. Will installing I noticed it would tought the plate that touches the firewall from inside the car. This plate is part of the pedal assembly. In the end, I had to remove knuckle from behind steering wheel and using a dremel was not necessary but the extra room will make sure I won't hear squeaking of the shaft touching the plate. Only issue is the rubber boot to protect water and debris entering the car. I just had to modify it to seal the hole. Regarding the PS lines, you just have to bend the one from the PS pump to the rack, the one with the 19mm banjo bolt. Not hard but just make sure it does not hit the steering knuckle. So in conclusion, not hard, you need spacers and you might have to dremel a little of the opening you have to modify the rubber boot or seal it with something else.
If you have questions, I can help. Going tomorrow for alignment but sure feels nice with a quicker turning ratio.
