charging of 2 camper batteries with truck alternator?

I had a '91 Jeep Cherokee, and the regulator function was part of the ECU. It made up grades over the older Delco alternator tricky,as my son found out on his '89. Delcos didn't 4x4 well. My wife had a later Cherokee that overheated. We did the new rad, water pump, head gasket, etc. It still did it. Looking back on it, the culprit was likely the ECU or the wires or the sensors.