John,
Welcome - I feel sorry for you not getting any responses. So I thought I'd have a try and offer what I can.
1. I don't know the colours (not a good start - but see 4.) The wires should go to the single washer pump on the washer bottle. If it's a single pump, you'll find that it runs forward or reverse direction for the front/rear washers.
2. On the Tipo (and FIATs in general) the central locking control unit/relay is not housed in the fusebox. Usually it is somewhere above the fusebox under the dash on the driver's side. I would expect the casing to be about double relay-size. The question to ask is: why are you trying to find it? They do not often fail, and I would suggest that if you have central locking problems the best place to start is to try and localise the fault to one door motor/switch (e.g. does it lock from the other side?) or wire (e.g. does the system immediately unlock all just-locked doors because it 'thinks' a switch is up, but really the wiring through the door pillar is broken?)
3. White/grey smoke is nothing to worry about as you have described it. White 'smoke' is simply condensation of water vapour (all engines do this, sometimes all the time on a cold day). Grey smoke - presumably to do with it being a diesel, I think it would be normal to have small amounts of visible fumes with a cold engine because the injectors will be injecting a little more fuel (to avoid hesitation problems) than when the engine is hot. If, however, your grey smoke is combined with difficult starting, then I would suggest that you check the glow plugs. Test that they are supplied with voltage (fuse, relay etc. may have failed) and remove glow plugs to check for visible damage. Examples I have seen were self-evident as 'not-working'!
4. I think when you say 'motor' you mean 'whole car' - as they seem to say over there
I can't help, but check the recent messages in this forum for the Porter manual available (illegally!) online. Also consider buying Haynes manual from Halfords. Quite a lot of the wiring will be common between all models, e.g. your windscreen washer question above.
If on the other hand you meant 'motor' then I apologise
I have a sneaking suspicion that there are no Tipo manuals that cover the diesel engine!
5. No idea. But find your local Lancia Delta Integrale specialist... those cars seem to have a cult following these days. They have a 2L twin-cam FIAT-derived engine bolted to a four-wheel-drive transmission. I'm sure, with a bit of lateral thinking, you could incorporate a diesel engine (of course, I personally couldn't possibly comment).
I refer you to that Top Gear episode (we get that over here but delayed a year or so!) where Richard Hammond and James May were sampling the sounds of the country side - birds singing, cows mooing, roosters crowing... "and here's another sound of the country - RIGADIGADIGADIG - a Massey Ferguson tractor!" The sound was, of course, emanating from their diesel Volvo convertible. *Diesel* I mean, really!
Earlier this year though, we had the diesel Jaguar make its debut, so I have to admit that you are in good company. Here in NZ we would not dream of importing such a model, yet our diesel fuel is considerably cheaper ($0.75/L vs. $1.15/L) balanced out by 'road user charges' apportioned by the km (i.e. higher "road tax" as you would say).
Anyway I have seen on the 'net that someone has made a 4WD Tipo, so it is possible but quite frankly you'd be better off starting with a Delta Integrale (or even maybe a Panda 4x4 combined with an Uno Diesel - that would be a lot cheaper!)
Good luck and hope you get a more useful response,
-Alex
