Don't know about the 87 but if you are using the 2000 alternator, 2000 Dakota/Ram, the charging system is computer control.
My sister had one that was having charging issues. We found out that under the battery box was a temp sensor that told the alternator/regulator how much voltage to charge the battery. We replaced the sensor and all was normal.
That's all I know about 2000 Dakota's.Just a FYI.