OK, Here is the real scoop on the V-864. The non modulated version of this engine WAS installed in the 1980 model. Apparently all of the electronics were not worked out yet. In 81, they went full force with this thing. It had digital fuel injection, electronic on-board diagnostics AND an analog back-up computer if anything went wrong.
I found the system to be very reliable and drove my 81 Fleetwood 330,000 miles with NO trouble. As a matter of fact, the second owner of this car since I sold it is STILL driving it. The only thing he has replaced on the motor is the distributor drive gear. 420,000 miles!!!
As for disabling the system, this is very easy. The key is knowing how the thing works to begin with. The computer measures load/torque requirements and when conditions are right, begins to shut off cylinders. This is accomplished by rotating a turret shaped contraption above the rocker arms allowing the rocker to raise up from the head. This action leaves the valve closed on that cylinder. With the valve closed, the same air/fuel mixture is continuously re compressed, keeping the cylinder temperature up and of course, not taking in any more fuel.
The key is that NONE of this happens until the car is at cruising speeds. This was determined by a signal from the transmission that it was in high gear. To disable the system, reach under the car and from the driver's side and snatch the 2 wire connector from the side of the transmission... you now have a full time V8. No codes, no lights, no problem.
Now what I did that I thought was a bit more elegant was to intercept this wire with a switch at the dashboard. It is simply a ground signal to the computer so no fancy voltage crap is required... just splice and go. With the switch in place you can run V8 as much as you want and then when you get stuck in the middle of nowhere looking for a gas station you can flip it on and return to the "32 mpg mode"
As for the complaints from the general public... hell it was new and everyone complains about that. At the time, American cars with 4 cylinders engines just were not good PR, especially in a Caddy. The other problems again had to do with the operation of the system. When you got up to moderate speeds the car would shift from 8 down to 6 and finally to 4 cylinders. The 6 cylinder mode was unbalanced feeling even though it was only in this mode for short periods of time. I think they would have been bettter off to have it drop from 8 to 4 like they do now. (YES, this is how today's Northstar engine handles driving without coolant, exept both valves are OPEN instead of closed) The other thing that made driving this a bit uncomfortable was the fact that when you coast to a stop, there is always that point when the governor in the transmission shifts down from 3rd to 2nd gear. In most automatics, you never feel this happen. At this point the engine was instantly returned from 4 cylinder operation to 8, creating a slight surge even at zero throttle. If you are not comfortable with the car and have a really light braking foot (typical 70yr old demographic) this could be scary.
Remember that the 368 is just a smaller bore version of the bulletproof 425 engine used from 77 up to 80. Buy the 81, complain about the V864 to get the price down, take it home, snatch a wire, and drive the hell out of that car. It will do good for you. If you really want something good, hold out for a Fleetwood Coupe. These things are getting REALLY rare.