The Computers used on FMJ's are not as fancy as ones used today. They are also not as easy to diagnosis as well - sense you can't talk to them, like you can with today's automotive computers.
All of the FMJ computers automatically the ignition timing - which is a good thing.
The newer FMJ computers also control the carburetor fueling ratio (somewhat) - which is mostly independent from the ignition timing control.
Part of computer controlled carburetor problem is the range of computer control - which came about before Ethanol came out. Depending on the alcohol to gasoline ratio (which varies) can be about 10-15% alcohol to 85-90% gasoline. The non-computer controlled carburetors, like my '77 wagon, has no mechanism to cope with Ethanol and runs bad with it. It feels like my 132 HP drops down to maybe 100 HP. It is noticeable, but mostly because the car has no way to cope - without changing the jets for the increased fuel needs.
The Chrysler computer controlled carburetors have some flexibility and can alter the fuel needs up about 5% or down about 5% (about a 10% swing, total) - which is just not enough for the increased fuel need for running the increased fuel need that Ethanol requires. That said, both of the FMJ versions (non or computer controlled carburetors) will run on either 100% gasoline or Ethanol, but neither very well. The computer controlled version a bit better than the other, but not but much better.
Getting back to my point, my '86 Fifth Ave (318 2-bbl) originally came with a Holley 6280 (the computer controlled version of the Holley 2280). It has been replaced with a Chinese knockoff Carter BBD and it works wonderful. The Lean Burn computer is controlling the ignition system just fine and it also "thinks" it is controlling the carburetor as well - but it is not.
Now getting back to your situation, You can change out the existing carburetor with a non-computer controlled version (Carter BBD, Holley 2280, or even any version of a 4-bbl) and leave the existing ignition system in-place and it will get along fine (providing one is not breaking any state or local laws by doing such). Changing the ignition system to a more simple changeover will work as well, but to be honest with you, a properly working computer will work so much better (in all situations) than the simple ignition system will - except until engine reaches "operating temperature". Then Lean Burn senses engine is "cold", it reduces the engine power level down by adjusting the ignition timing down, until it gets warm - which is also a great idea. An irritating thing, but it is best for the engine.
The only thing different about police vs. non-police car computers was the computer moved from the air cleaner to down by the parking brake petal under the dash. The computer programing is not any different between the two versions (or if it is, it is very minor). All in all, computers (in general) don't like water moisture, heat and vibration - so by having it mounted on the air cleaner, above the exhaust manifold, you have the heat, the vibration and to some extent, water moisture, all there. That said, the Chrysler computers used for FMJ's had very little problems, for the most part. About 95% of all Lean Burn computer problems were not even computer (or computer sensor) related. That 95% pointed to other things (like loose timing chain, faulty spark plug wire, stopped-up catalytic converter, and so forth).
Actually, I think the 95% number might be closer to maybe 99% (being problems were elsewhere).
Now the computer system used for today's are a lot more problematic - and mostly with sensors more than anything else.
BudW