Dual spark plugs per cylinder adds more power, always has, was just hard to do that with a distributor, and space/access in a head for a 2nd spark plug was also an issue, especially on V6/V8 engines
Aircraft engines pretty much all use dual plugs for more power but also safety reasons, they run separate dual spark systems, both are used for take off and landing but only 1 while in flight, just in case..............
DIS eliminated the distributor complication
4 valves per cylinder added even more power, and better efficiency, also better use of head space so dual spark plugs were replaced with 4 valve engines in vehicles, aircraft engines still used dual spark plugs for safety and power
2.3l SOHC Lima engine was introduced in the 1974 Pinto and used in several Ford cars thru 1988 with 4 spark plugs
You don't really need to change the head unless its cracked, you can just run it with 4 working spark plugs and 4 dummy plugs
The distributor hole in the block was deleted in 1990/91 castings I think
So if you have the hole then you can use a distributor
DIS modules get very very HOT
So they need a Heat Sink
A heat sink is a piece of metal that can dissipate heat faster than the smaller case on the module, spreads the heat out over a wider area
Heat sinks often have fins to increase their surface area
TFI module heat sink looks like this:
https://i.ebayimg.com/images/g/FEYAAOSwHepjT~-u/s-l1200.jpg
And like this with TFI module in place:
https://www.supermotors.net/getfile/832641/fullsize/idm-ignition-002.jpg
ICM 2.3l DIS was mounted to the lower intake metal to use it as the heat sink and its location is also just behind the cooling fan so constant air flow when in use
With any heat sink you must use a thermal paste between the module and heat sink to increase the heat transfer, air gaps are BAD, lol
Applying the paste seen here:
https://postimg.cc/3dM5SWgT