Rod knock isn't "common" with the 2.3. Some engines live harder lives than others.
As a minimum, you'd have to pull the crank & have it machined down .010. The new bearings would be - .010 to fit.
You may also need to have the big ends of the rods re-sized if they have gone out of round.
The voltage regulator may be on the way out. It may fail soon or, like my work truck, last a long time. It's one of those things that can't be predicted.
Go to the Ranger and B-Series board. The third post there is a "sticky" called "Technical Information". Click on it and scroll down to "Pulling EEC-IV Codes". It would stand to reason that there's a faulty sensor or other part that is causing the irregular idle problem.