Generally EFI ignitions are very good and even handle mild mods but what sort of volts does an EB2 4.0 EEC-IV putout.....I imagine in the vicinity of 30-40KV??? Will a 4.0 gain anything/much from a high out coil???

Have to be careful not to overload the ignition circuit of the ECU. Don't know if theres much gain anyway, only if you were running 11:1 compression or better. The more compression you got, the harder it is for the spark to jump.

I spose an engine analyser would tell/show me how much load is on igition too huh??? What KV can the ECU handle???

Don't know, but when on the engine anylizer, the amount of spark Kv shown is what it took to fire that particular plug at that time. The only way to see what Kv the coil is puting out, is to remove the HT lead, while idling, but still allowed to jump to the plug, this makes the coil work harder, you should see the Kv rise. You could keep increasing the gap until it misses or starts to jump to the head or manifold.
Let us know how you go with this.

Typically these 'high performance' coils draw more current from the ignitor. This can cause it to fail so keep the primary resistance/inductance close and you should be able to change coils safely.

The ECU doesn't see the high voltages at all, regarless of what coil you are using. It simply sends a low voltage (approx. 5V) signal to the TFI module. This module switches 12v (actually switches the ground) to the primary winding of the coil, creating a magnetic field.

When the primary current is stopped, the magnetic field breaks down and a high voltage is generated in the secondary winding of the coil and sent to the distributor. The coil is actually working as a generator, where a conductor moving through a magnetic field generates a voltage. The current turning on then off has the same effect as moving the magnetic field, which is the same as moving the conductor (Can you tell I am an electrical tech head ???)

The TFI ignition from Ford is an excellent system, and I doubt you'd notice any better performance on all but the hottest engines (we are talking about street engines here). I had originally intending fitting TFI to my Clevo, but getting a dizzy to fit was not as easy as it looked.

Don't waste your money. If you want to spend money on the ignition a good set of leads and some platinum plugs would probably serve you better.

A Crane Hi-6 or MSD digital 6 make a noticeable difference.
Raiki; a TFI dizzy from a 460 will drop straight in to a cleveland if it's and early block or you'll have to get the tip precision ground to fit a in a late block. A 351w TFI dizzy will also fit but just needs the gear changed to a Cleveland type.

Cheers,
Pete.

Even on a bock stock engine? ... or are we talking basic mods first, such as cam, exhaust, etc.

Pete, I knew that but it ended up easier and cheaper to fit the Crane XR3000 system to my Mallory. Looks nicer too (still looks old school). I have a late block (black).

oh hell yeah on such an engine.
i fitted a an MSD DIS-4 plus to my ef and it picked up 1mph and droped .3sec with no other changes

Yes even on a bog stock engine.