So, i can help a bit. I did install my HEI, on a feedback computer carbed 300. Except someone long ago had already done some work. It was set up with a standard 4bbl holley and a points and condenser distributor, with a pertronix ignitor in place of the points. There were lots of hacked wires. So my install is different than someone starting with an uncut wiring harness.
My setup has a Davis Unified Ignition HEI. It has 12v power supplied by a 300Amp golf cart relay, drawing right off the battery. This is fairly standard for every install.
On my hacked up wiring, i had issues, so i run the ignition off a toggle switch in the cab. The switch turns on the golf cart relay, which turns on the ignition/distributor. Then i use the key to engage the starter. When i want to shut the engine down, the key no longer works, and i have to use the toggle switch mentioned above. Thats all there is to it.
On an un-hacked wiring harness, you will wire the distributor to the relay like above, but instead of a toggle switch, you must locate the ignition switch on the lower end of the steering column. Not the key cylinder... On that ignition switch, you will have to probe to find a single wire that gets 12v when the key is in BOTH the start
positions. With my hacked up harness, i couldnt find one.
Otherwise, thats all there is to the HEI. No extra modules are needed. I cannot comment as to whether you can remove the EEC completely and not have other power functions continue to work. My bronco has no power anything or AC.
The other option, is the Ford DuraSpark II ignition. This is what came on the 82 and prior ford engines, back to whenever the got rid of points ignitions. There are kits available and lots of documentation online on this conversion. Going this route has benefits over the HEI. Replacement parts can be bought at any parts store by getting stuff for a 1976 ford vehicle with your engine. Its also very reliable. The cons to this route are minor. It does not start quite as quick as HEI, nor does it provide quite as much spark. But these are very small differences and both will be a VAST improvement over the feedback ignition and carburetor systems.
Then its as simple as bolting whatever intake and carb you want on it. Though i cant comment on cruise control. Remember... my 85 is a bare bones base model. It didnt even come with a radio!
may be able to provide a bit more info.