It is common to fail regulators on these, the diode fail causes field to get bumped up higher since not enough output, regulator dies from overheating trying to do it. Per several major rebuilders when asked for highest fail parts in their 6G rebuilds. I've had a failed regulator on almost every one I've personally rebuilt too.
You can instantly tell the commonly used Transpo F601 from the F601HD (heavy duty) regulator since they are stamped with part number on them. On Focus you can read which one is in alt by use of a small flashlight and looking up in cooling grille to regulator face. Yes, more than one 6G regulator, color coded.
I rebuild my own and do use that better rectifier assembly and love it..........I doubt seriously if the field or stator windings ever show much trouble, I certainly haven't found any. I mod the plastic backside bearing retaining 'tolerance ring' so alt can be pulled back apart later without tearing it up and I can reuse it.