This is what I have:1992 Nissan 240sx SE KA24DE w/Super HICAS
Block, Complete Head, Intake Manifold, Throttle Body, Top Engine Harness, Power Steering pump, Power Steering high pressure Line, Wastegate solenoid controller, Lower Engine/transmission harness, Turbo exhaust outlet extension, Turbo inlet pipe, Turbo outlet pipe, Wastegate actuator, Cam Angle Sensor, Bell housing bolts, Exhaust Manifold, Alternator, Starter, Fuel Rail, Injectors, Canister, Turbo, ECU, 5 Speed RWD Transmission, Clutch, Engine Wiring Harness, Ignitor Chip.
Questions:Do I NEED and intercooler? If so, would a cheap SMIC or TMIC suffice?
Do I need to replace the radiator? I heard the KA rad/fan housing will not work with the SR.
What other costs am I forgetting? With what I have so far, what do you think the total cost of installation from this point on will be?
What else would I need?
Your going to need the p/s pump and bracket from a Hicas model sr if you plan on keeping it active (the hicas). If not, there will be no line pressure going back to the hydraulic unit and I would suggest replacing it w/ a lock bar or fitting in a 3mm washer between the lock nut and the stroke stopper (names from FSM). That is unless you want your toe changing +/- 1 degree at random. 
No you don't need an intercooler, but it's HIGHLY recommended.
You don't need a different radiator either, but again, it's HIGHLY recommended. You will need an electric fan though (unless you have the sr shroud) and (some) new hoses.
No you don't need an intercooler, but it's HIGHLY recommended.
You don't need a different radiator either, but again, it's HIGHLY recommended. You will need an electric fan though (unless you have the sr shroud) and (some) new hoses.
While your at it, you might want to replace your clutch. Easier to do when the motor and transmission is out, but it isn't necessary. Also, you forgot to add coilpacks (4) and the coilpack harness. You also forgot to add an intake. As for the intercooler, it would be very beneficial if you had one, but as Dori Dori said, you actually don't need one. Also, TMIC will not work as you will not have enough hood clearance. You'll either have to get a FMIC or SMIC or go with the setup that the Signal Twins use (Which I might point out is VERY nice!!). Everything, else has been covered my Dori Dori. Oh yeah, you'll also need misc gaskets and hoses (for the heater especially). Hard to gauge the total costs as prices vary. Also if your planning on doing this yourself and so forth.