as above, will be a pretty big job, so you'd want full access to a 147/156/GT with all the spares (eg: 'wrecked' car).
the clockspring is the junction point between the SW and the SW column, where the SW 'spins'. it has multipin plugs on the SW-side to connect up the airbag plus accessories (horn, SW controls for stero), and a multipin plug on the otherside to connect to the wiring loom. it's at this point (wiring loom coming up the steering column) you would need to customise the connections i imagine.
*horn: should be existing wiring for this
*airbag: if your car has an airbag, then there should be existing wiring for this
*SW controls for stereo: i don't know the details, but you will need to feed power (it's either +12V or +5V) 'to' the wheel controls to make the backlighting of the buttons work and allow the buttons to function; then 3 wires feed back away from the SW to the headunit which are 1. GND 2. 'L-side buttons' wire 3. 'R-side buttons' wire; the L/R wires 'float' at +5.00V (ie: voltage difference between these wires and GND is 5V); you then need a headunit compatible with SW control inputs, and probably an interface to 'translate' the alfa voltages to voltages that the new headunit 'understands'
*cruise: not possible because it relies on multiple input/output sensors including electronic throttle control; i figure the 145 does not have an 'electronic accelerator'; but you could fit an aftermarket unit that integrates with the 'accelerator cable' and if you're an electronics whiz, you may be able to replace the aftermarket stalk for the original alfa one
so to achieve all of this, you'd need to understand the autoelectrics and electronics of your car and the donor, have all the necessary wiring diagrams, all the parts, and be able to join them together.
hopefully that's easy for you, though if you're asking here, i suspect maybe not. i'd have no idea myself!