I'd rebuild the original unit, same basic deal as a non-computerized carburetor, just has an M/C solenoid and TPS. The airhorn has an airbleed deal that needs a couple of seals, otherwise, not much different anyplace than a older style unit.
If the service engine light isn't staring him in the face, put the stock M/C solenoid and TPS back in the carb during rebuilding. The TPS is very easily broken when putting the airhorn back in place if you aren't careful, otherwise, it's just another carb build.....Cliff