Thanks. All the sensors were replaced for this project. The 83 had the 305 4bbl also. There's no gas smell coming from the exhaust and from what I can determine, it's getting real good gas mileage.Sounds to me like you might've lucked up and are able to run the car with the basics at least. If you're getting a code 41, then SOMETHING is setting the code, although for some reason it's not puting you in limp home mode. IIRC, a code 41 by itself will go pig rich with locked base timing if you don't also have a Code 12 set. A Code 12 will not set. But the 41 will. Your reference signal is coming from the "R" terminal of the ignition module, through the "B" terminal of the distributor harness to ECM. A white/purple wire going to pinout #10 on the back of the ECM.
There may be peripheal equipment that isn't sending or getting any signals to the ECM. This MIGHT make it do weird things.
The 83 ECM is NOT 100% compatible with the 84. It just isn't.
A code 41 setting with key on and engine not running may mean your MAP or differential pressure sensor (VAC, aka D/P sensor) to the manifold is showing a running voltage when engine is off. Meaning the sensor could be hosed.
This is all based on an 84 307 5.0L troubleshooting procedures. GP SHOULD have the same, but the CSM would have the right info in it.
But if you like it, then go with it.