This shouldn't be too difficult to sort out.
If you have a wiring diagram for the older wiring, compare this with a wiring diagram for the later model as regards the column switch wiring,
then check which colour wires are present on both column switches and then see which wires don't correspond and figure out where these should go.
You might be able to use a multimeter (set to ohms) to determine the wire colours you're uncertain about, go to which part of the column switch.
In my experience on older Fiats, each wire colour indicates a specific purpose e.g. green and grey go to the headlamp dip and main beams (or possibly vice-versa), light blue and light blue+blk tracer go to the right and left indicators etc. The wire to the horn push is usually black (or possibly purple on later models), this wire is connected to earth (ground) when the horn button is pressed. (you should be able to see the colour of wire used at the horn button contact on the column switch).
There's maybe 7 or 8 wires normally used - one wire for the horn, one wire to feed the indicator selection switch, 2 wires leaving the indicator switch to feed left and right indicator lamps, one wire feeding the headlamp beam selector switch, 2 wires leaving the h/l switch to feed dip and main beam h/l's and possibly? another wire to allow for 'flashing' the main beams. The live feeds to the indicator and h/l switches probably come from the fusebox.
If you're still unable to figure out the wiring, maybe post a list of the colours of all of the wires on both old and replacement switches and we'll try to help further.
