Worth a try
Yes, 2.9l TFI setup would work on the 4.0l, same distributor setup and oil pump drive, from what I am seeing
As said 2.8l distributor wouldn't work, that comes up on duraspark conversions for 2.9l
2.9l and 4.0l used same firing order
Yes, use larger injectors to "trick" the 2.9l computer into thinking its still running the smaller engine and feeding it the same amount of fuel as before
i.e. at say 2,500rpm the computer was opening 2.9l injectors for 100milliseconds to get 1gram of fuel, to get good O2 sensor feed back
Larger injector would flow 1.2gram instead, as an example, computers none the wiser
This prevents computer setting constant Lean code
Not sure what the stock size was for the 2.9l and 4.0l, if 4.0l was larger then might work as is
2.9l used a MAP sensor system, and intake vacuum is universal on gasoline engine, so no issue with size there
Not sure on exhaust size?
You would have to check diameters
Same for radiators?