I have done this conversion to 2 of my previous 128 coupes. If you can find a 1500 engine used in the fiat strada or ritmo, all you would need to do is fit your 128 engine mounts, and it will bolt straight into your 128 engine bay. You could also use the x1/9 engine, which is the same engine, but has a different sump and oil pick-up. I understand that this is because the engine leans at an angle in the x1/9 bay, so would recommend using the strada type sump and oil pick-up to ensure no oil starvation! Note-the 128 oil pump and pick-up is apparantly different, so I suggest you don't swap them over! I fitted electronic ignition from the uno 1300, and fitted a fast road cam and weber 34dmtr carb, and it went like the wind! I also tried twin weber carbs, but found that the car lost all driveability for everyday driving, being either stop/or flat out, which is no fun. You could even use the lancia delta 1500 sohc, as it is also the same engine, again, utilising the 128 mounts. You may want to use the 5 speed gearbox from the strada/ritmo/delta, as the 128 4 speed is too low geared really. The gearbox bolts straight in, with very minor mods to drive shaft ends. 128 gear linkage can be used, but you will have to 'press down' to change from 4th to 5th, which is a bit quirky but still worthwhile imo.