In the 1950s there was a trucking company in Nashville Tennessee that used my father's shop for all their electrical system maintenance. This was long before alternators were in general use, so those rigs ran very large Delco-Remy generators and 6-unit regulators that were about 6 inches square. Generators and regulators were rebuilt, paired up by serial number, and changed as a matched pair on a mileage and/or hourly basis. Dad rebuilt the generators and regulators and adjusted them to factory specifications on a Sun generator/regulator tester, and the company kept the paired units in inventory for specific trucks. Their maintenance supervisor said that charging system failures on the road were virtually nonexistent once that program was instituted.
Maybe "matching" components isn't necessary, but it's certainly effective.
Jerry
