To me, if I was looking at a Lean Burn car, I'd look FIRST to see if anybody had mucked with it! Many would get a reman distributor and a reman carb, both of unknown/verified specs, and the result generally was not good. Many fine Chryslers were ruined by those poor conversions, by observation.
The first '76 LB C-bodies I saw at the dealership sounded fantastic. Instant throttle response off idle, more energetic, quieter, AND no catalytic converter was needed@! Hence the "Non-Catalyst" sticker on the lh door shell. THAT impressed me as GM and Ford were struggling with AIR pumps and massive amounts of delay valves and such in their underhood equipment to get th engines past emissions.
The "lean" part was that the carb would meter a 16.0 A/F ratio at cruise, rather than 14.7. At that leaner ratio, CO and HC were basically zero, as NOx was a little higher, but NOx was not a federal emissions spec at that time. In order to get the learner mixture fired-off, the computer had MORE spark timing in its map. Chrysler, as usual, was building a more efficient motor, it appeared to me, which I liked. But it might well have been that it was "too far, too fast" for good reliability AND understanding of how it all worked by the people who were working on them (outside of the dealer network). Back then, by observation, the repair shops were usually a little quick to condemn something they didn't then know anything about. Two years later, they DID know and they WERE working on them in their shops. by observation.
The whole system worked on voltage and resistance. The Chrysler "magic box" tester was not required, as it seemed that they failed more than they passed, to me. We got a Volare used car in the shop with a suspected Lean Burn problem. I found a Chilton Aspen/Volare book with a diatnostic of the system in it. I gave it to the tech and he got his meter and went to work, finding the issue and fixing it. GROUNDS are important, too!
There were a few Chrysler TSBs to re-locate the computer into the passenger compartment. Probably more needed in B/RB police cars than on a 318/360, I suspect. But I digress.
To me, the best "change" would be a Mopar Perf electronic ignition kit (or similar, which gets you a new distributor with a good timing curve) and some kind of new carb (Holley 4175 spreadbore for a Chrysler B/RB application) or a Edelbrock AFB/AVS (with a matching intake manifold). This way, you KNOW what the timing specs are on the distributor AND the metering specs of the carb being used. You just don't have that information on any reman parts, by observation, where the parts are more "will fit and work" rather than "fit and work as well as they can".
At some point in time, if it hasn't already been reached, I suspect the orig Lean Burn computers will not be remanned any more, unless somebody wants to "un-pot" the circuit board and re-touch the solder joints and such so everything works well again. Many of the sensors are probably already gone, I suspect. So . . . doing the electronic ignition upgrade and carb change might be planned on. One of those deals, if you know where you're eventually going to end up, why not get there sooner and be done with it?
Enjoy!
CBODY67