Alternator overcharging

14.3!!!! volts is a very normal charging voltage, well within the normal range.
I presume your voltage with the first (overcharging) alternator was in excess of 15.5 volts, which after a short while will start "cooking" the batteries and producing that sulfer smell.
I would say the present alternator is acting normal.

When the first tech checked the alternator, he probably didn't check it at anything but idle. It should also have been checked at 1500 rpm.

 

14.3 v is normal. Mine is always between 13.7 and 14.3 when motor is running.

 

Yes, I think the damage was done before you replaced the defective alternator.
Normal charging voltage will typically range from 13.5 to 14.5 (or even slightly higher +.3). In hot/warm weather it typically charges at less voltage, but in frigid/cold temps it requires a higher charging voltage. If the rotten egg smell persists, have your batteries load tested and checked, as well as checking alternator voltage at high rpm (1500-1700).

Normally, when the regulator goes bad, the alternator puts out its unrestricted voltage, which often is up to 16-18 volts or more.

 

I had a freightliner charge 19.5v lol but it was 13.5v when idle. had a bad regulator in the alternator. but by the time i fixed it after experimenting at idle it burnt up some regulator by the batteries. BTW ruined the 4 batteries i had in it.