First of all sorry for my English.
Yesterday my Golf MK4 1.4 16v (1999) had a problem so today I took it to the mechanic. When he checked the car he found out that the timing belt is broken so the entire engine is gone. Now I have to buy another engine to mount on it and I'm searching for a used engine. The 1.4 is hard to find so everyone i asked told me they have the 1.6 version. My mechanic is not that sure but he said that the version 1.6 cannot be mounted on my car because it may have different electric plugs and different cabling system that may not work with my ecu. Another guy told me that nothing change between the two versions and it fits like the old one (1.4). Now before someone tell me to sell my car and get a new one, I need to specify that i spent so much money on it that if I sell it now I will not get even half of the money I spent. A month ago I installed the LPG system so I really need to fix that car. So can I get the 1.6 and mount on it or I have to keep looking for the 1.4 version?
You should make a list of broken parts and try to figure out if it is cheaper to replace them or is it cheaper to get a new engine and take risks.
Broken timing belt will bend the ventiles mostly, and not all of them, because the ones which were already closed will not be bend. It may cause other damages too but I strongly recommend checking the parts first, it is easy to open the top of the engine :)
Please let us know exactly what parts are broken also. By the way, how old was the timing belt and when did you check it last time before break? AFAIK VW does not have any replacement timetable for this models, it just says check after every 30k KM if I remember correctly.
For example the ventiles are 5euro each. http://www.ebay.de/sch/i.html?_from=R40&_trksid=p2047675.m570.l1313.TR8.TRC1.A0.H0.Xvw+1.4+16v+ventile.TRS0&_nkw=vw+1.4+16v+ventile&_sacat=0
There are two types of 1.6 engine fitted to the Mk4 Golf, the SR (8v) and the 16V. Either engine will physically fit in your car and they all use the same clutch and gearbox (02K I believe, I assume you have a rod change box?)
Ancillary and loom wise, these are all the same too. The Mk4 Golf uses a standardized loom so all of the sensors should be plug and play.
Where you get issues is that you probably need not just the engine but matching ECU, clocks and keys because the fueling and ignition timing is all specific to the engine fitted. On the Mk4 platform cars, the clocks are paired to the ECU and the transponder in the ignition key is paired to the clocks.
That said, I recently bought a Mk4 Golf 1.6 SR needing a clutch for a couple of hundred pounds and something like that would give you all the components you would need. You can also use a 1.4 16v from a Polo, a Seat Arosa / Ibiza / Cordoba, Audi A2 and some Skoda so that may make finding another engine easier.
One final note, it is worth popping the cylinder head off your existing engine. You may find you just need a couple of valves and a gasket set. Don't write it off until it's properly stripped.